diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 00000000..218b5ddf
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,52 @@
+name: CI
+
+on: [ push, pull_request ]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    continue-on-error: ${{ matrix.env.experimental == true }}
+    strategy:
+      fail-fast: false
+      matrix:
+        env:
+          - { php: 7.4 }
+
+    env: ${{ matrix.env }}
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+
+      - name: Setup PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: ${{ matrix.env.php }}
+          tools: composer
+          extensions: pdo, sqlite3
+
+      # composer
+      - name: Update Composer
+        run: |
+          sudo composer self-update
+          composer --version
+      - name: Validate composer.json and composer.lock
+        run: composer validate
+
+      - name: Cache dependencies
+        uses: actions/cache@v1
+        with:
+          path: ~/.composer/cache
+          key: dependencies-composer-${{ hashFiles('composer.json') }}
+
+      - name: Install dependencies
+        run: composer install
+
+      - name: Check coding style
+        run: composer lint
+
+      - name: Run Unit Tests
+        run: |
+          echo "Running unit tests with $(which php)";
+          .Build/bin/phpunit --colors -c .Build/vendor/nimut/testing-framework/res/Configuration/UnitTests.xml Tests/Unit/;
diff --git a/.gitignore b/.gitignore
index ff5a085e..6ad5a38c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -5,3 +5,5 @@ vendor/*
 /composer.lock
 /.Build
 /.php_cs.cache
+/.php-cs-fixer.cache
+var
diff --git a/.php_cs b/.php-cs-fixer.php
similarity index 100%
rename from .php_cs
rename to .php-cs-fixer.php
diff --git a/.php-version b/.php-version
new file mode 100644
index 00000000..37722ebb
--- /dev/null
+++ b/.php-version
@@ -0,0 +1 @@
+7.4
diff --git a/.travis.yml b/.travis.yml
deleted file mode 100755
index c95fd82f..00000000
--- a/.travis.yml
+++ /dev/null
@@ -1,46 +0,0 @@
-language: php
-
-os:
-  - linux
-
-dist: "xenial"
-
-jobs:
-  fast_finish: true
-  include:
-    - php: 7.4
-      env: TYPO3_VERSION=^10
-    - php: 7.3
-      env: TYPO3_VERSION=^10
-    - php: 7.2
-      env: TYPO3_VERSION=^10
-    - php: 7.2
-      env: TYPO3_VERSION=^9
-addons:
-  apt:
-    packages:
-      - parallel
-
-cache:
-  directories:
-    - "$HOME/.composer/cache"
-
-before_install:
-  - composer self-update
-  - composer --version
-
-install:
-  - composer require --no-update "typo3/minimal:$TYPO3_VERSION"
-  - composer require --no-update "solarium/solarium"
-  - composer install --prefer-dist
-  - export TYPO3_PATH_WEB=$PWD/.Build/Web
-
-script:
-  - >
-    echo;
-    echo "Running php lint";
-    find . -name \*.php ! -path "./.Build/*" | parallel --gnu php -d display_errors=stderr -l {} > /dev/null \;
-  - >
-    echo;
-    echo "Running unit tests";
-    .Build/bin/phpunit --colors -c .Build/vendor/nimut/testing-framework/res/Configuration/UnitTests.xml Tests/Unit/
diff --git a/Classes/Controller/SearchController.php b/Classes/Controller/SearchController.php
index 26586558..234d8c66 100644
--- a/Classes/Controller/SearchController.php
+++ b/Classes/Controller/SearchController.php
@@ -39,20 +39,11 @@
 
 class SearchController extends ActionController
 {
-    /**
-     * @var array
-     */
-    protected $requestArguments;
+    protected array $requestArguments = [];
 
-    /**
-     * @var ServiceProviderInterface
-     */
-    protected $searchProvider;
+    protected ?object $searchProvider = null;
 
-    /**
-     * @var \Psr\Log\LoggerInterface
-     */
-    private $logger;
+    private \Psr\Log\LoggerInterface $logger;
 
     public function __construct(LogManagerInterface $logManager)
     {
@@ -79,6 +70,7 @@ public function detailAction(string $id)
                     )
                 );
         }
+
         $this->addStandardAssignments();
 
         $this->view->assignMultiple($detail);
@@ -103,9 +95,7 @@ public function indexAction()
                     $this->settings,
                     null,
                     $this->searchProvider->getRequestArguments()
-                ),
-            false,
-            true
+                )
             );
 
             $this->addStandardAssignments();
@@ -124,7 +114,7 @@ public function indexAction()
     /**
      * Initialisation and setup.
      */
-    public function initializeAction()
+    protected function initializeAction()
     {
         ksort($this->settings['queryFields']);
 
@@ -132,6 +122,7 @@ public function initializeAction()
 
         $this->requestArguments = $this->request->getArguments();
         $this->requestArguments = ArrayUtility::cleanArgumentsArray($this->requestArguments);
+
         $this->searchProvider->setRequestArguments($this->requestArguments);
         $this->searchProvider->setAction($this->request->getControllerActionName());
         $this->searchProvider->setControllerExtensionKey($this->request->getControllerExtensionKey());
diff --git a/Classes/Hooks/RealUrl.php b/Classes/Hooks/RealUrl.php
index 3adcb481..82634b31 100644
--- a/Classes/Hooks/RealUrl.php
+++ b/Classes/Hooks/RealUrl.php
@@ -37,7 +37,6 @@ class RealUrl
      * Create automatic RealUrl Configuratoin.
      *
      * @param $params
-     * @param $pObj
      *
      * @return array
      */
diff --git a/Classes/Service/AbstractServiceProvider.php b/Classes/Service/AbstractServiceProvider.php
index 25f3ca06..c8bc50f8 100644
--- a/Classes/Service/AbstractServiceProvider.php
+++ b/Classes/Service/AbstractServiceProvider.php
@@ -8,31 +8,18 @@
 
 abstract class AbstractServiceProvider implements ServiceProviderInterface
 {
-    /**
-     * @var string
-     */
-    protected $connectionName;
+    protected string $connectionName;
 
     /**
      * @var LogManagerInterface
      */
     protected $logger;
 
-    /**
-     * @var array
-     */
-    protected $requestArguments;
+    protected array $requestArguments = [];
 
-    /**
-     * @var array
-     */
-    protected $settings;
+    protected array $settings = [];
 
-    /**
-     * @param string $connectionName
-     * @param array  $settings
-     */
-    public function __construct($connectionName, $settings)
+    public function __construct(string $connectionName, array $settings)
     {
         $this->connectionName = $connectionName;
         $this->settings = $settings;
diff --git a/Classes/Service/ServiceProviderInterface.php b/Classes/Service/ServiceProviderInterface.php
index 800e8a44..646ff2ba 100644
--- a/Classes/Service/ServiceProviderInterface.php
+++ b/Classes/Service/ServiceProviderInterface.php
@@ -32,11 +32,7 @@
  */
 interface ServiceProviderInterface
 {
-    /**
-     * @param string $connectionName
-     * @param array  $settings
-     */
-    public function __construct($connectionName, $settings);
+    public function __construct(string $connectionName, array $settings);
 
     public function connect();
 
diff --git a/Classes/Service/SolrServiceProvider.php b/Classes/Service/SolrServiceProvider.php
index d718f5c2..08f6902d 100644
--- a/Classes/Service/SolrServiceProvider.php
+++ b/Classes/Service/SolrServiceProvider.php
@@ -28,11 +28,15 @@
  * ************************************************************* */
 
 use Solarium\Client;
+use Solarium\Core\Client\Adapter\Curl;
+use Solarium\Core\Client\Adapter\Http;
 use Solarium\Exception\HttpException;
 use Solarium\QueryType\Select\Query\Query;
 use Subugoe\Find\Utility\FrontendUtility;
 use Subugoe\Find\Utility\LoggerUtility;
 use Subugoe\Find\Utility\SettingsUtility;
+use Subugoe\Find\Utility\UpgradeUtility;
+use Symfony\Component\EventDispatcher\EventDispatcher;
 use TYPO3\CMS\Extbase\Utility\LocalizationUtility;
 
 /**
@@ -40,66 +44,62 @@
  */
 class SolrServiceProvider extends AbstractServiceProvider
 {
-    /**
-     * @var string
-     */
-    protected $action;
+    protected ?string $action = null;
 
-    /**
-     * @var array
-     */
-    protected $configuration = [];
-    /**
-     * @var Client
-     */
-    protected $connection;
+    protected array $configuration = [];
 
-    /**
-     * @var string
-     */
-    protected $controllerExtensionKey;
+    protected Client $connection;
 
-    /**
-     * @var \Solarium\QueryType\Select\Query\Query
-     */
-    protected $query;
+    protected ?string $controllerExtensionKey = null;
+
+    protected Query $query;
 
     public function connect()
     {
         $currentConnectionSettings = $this->settings['connections'][$this->connectionName]['options'];
+        // Upgrading to Solarium >= 5
+        if (!array_key_exists('core', $currentConnectionSettings)) {
+            $currentConnectionSettings = UpgradeUtility::handleSolariumUpgrade($currentConnectionSettings);
+        }
+
         $connectionSettings = [
             'endpoint' => [
-                'localhost' => [
+                $this->connectionName => [
                     'host' => $currentConnectionSettings['host'],
                     'port' => (int) $currentConnectionSettings['port'],
                     'path' => $currentConnectionSettings['path'],
-                    'timeout' => $currentConnectionSettings['timeout'],
                     'scheme' => $currentConnectionSettings['scheme'],
+                    'core' => $currentConnectionSettings['core'],
                 ],
             ],
         ];
 
-        $client = new Client($connectionSettings);
-        if ($currentConnectionSettings['username'] && $currentConnectionSettings['password']) {
-            $client->getEndpoint()->setAuthentication($currentConnectionSettings['username'], $currentConnectionSettings['password']);
-        }
+        // create an HTTP adapter instance
+        $adapter = new Curl();
+        $eventDispatcher = new EventDispatcher();
+        $adapter->setTimeout((int) $currentConnectionSettings['timeout']);
+        // create a client instance
+        $client = new Client($adapter, $eventDispatcher, $connectionSettings);
+
         $this->setConnection($client);
+        $this->testConnection();
     }
 
-    /**
-     * @return array
-     */
-    public function getConfiguration()
+    private function testConnection(): void
+    {
+        $ping = $this->connection->createPing();
+        $this->connection->ping($ping);
+    }
+
+    public function getConfiguration(): array
     {
         return $this->configuration;
     }
 
     /**
      * Main starting point for blank index action.
-     *
-     * @return array
      */
-    public function getDefaultQuery()
+    public function getDefaultQuery(): array
     {
         $this->createQueryForArguments($this->getRequestArguments());
         $error = null;
@@ -107,15 +107,15 @@ public function getDefaultQuery()
 
         try {
             $resultSet = $this->connection->execute($this->query);
-        } catch (HttpException $exception) {
+        } catch (HttpException $httpException) {
             $this->logger->error('Solr Exception (Timeout?)',
                 [
                     'requestArguments' => $this->getRequestArguments(),
-                    'exception' => LoggerUtility::exceptionToArray($exception),
+                    'exception' => LoggerUtility::exceptionToArray($httpException),
                 ]
             );
 
-            $error = ['solr' => $exception];
+            $error = ['solr' => $httpException];
         }
 
         return [
@@ -124,12 +124,7 @@ public function getDefaultQuery()
         ];
     }
 
-    /**
-     * @return array
-     *
-     * @throws \TYPO3\CMS\Extbase\Mvc\Exception\StopActionException
-     */
-    public function getDocumentById(string $id)
+    public function getDocumentById(string $id): array
     {
         $arguments = $this->getRequestArguments();
 
@@ -168,27 +163,24 @@ public function isExtendedSearch()
 
         if (array_key_exists('extended', $this->requestArguments)) {
             // Show extended search when told so by the »extended« argument.
-            $result = (true == $this->requestArguments['extended']);
-        } else {
-            // Show extended search when any of the »extended« fields are used.
-            if (array_key_exists('q', $this->requestArguments)) {
-                foreach ($this->settings['queryFields'] as $fieldInfo) {
-                    if ($fieldInfo['extended']
-                        && array_key_exists($fieldInfo['id'], $this->requestArguments['q'])
-                        && $this->requestArguments['q'][$fieldInfo['id']]
-                    ) {
-                        // Check if the request argument is an array itself (appies to field type "Range")
-                        if (is_array($this->requestArguments['q'][$fieldInfo['id']])) {
-                            foreach ($this->requestArguments['q'][$fieldInfo['id']] as $key => $value) {
-                                if ('' !== $value) {
-                                    $result = true;
-                                    break;
-                                }
+            $result = ((bool) $this->requestArguments['extended']);
+        } elseif (array_key_exists('q', $this->requestArguments)) {
+            foreach ($this->settings['queryFields'] as $fieldInfo) {
+                if ($fieldInfo['extended']
+                    && array_key_exists($fieldInfo['id'], $this->requestArguments['q'])
+                    && $this->requestArguments['q'][$fieldInfo['id']]
+                ) {
+                    // Check if the request argument is an array itself (appies to field type "Range")
+                    if (is_array($this->requestArguments['q'][$fieldInfo['id']])) {
+                        foreach ($this->requestArguments['q'][$fieldInfo['id']] as $key => $value) {
+                            if ('' !== $value) {
+                                $result = true;
+                                break;
                             }
-                        } else {
-                            $result = true;
-                            break;
                         }
+                    } else {
+                        $result = true;
+                        break;
                     }
                 }
             }
@@ -246,21 +238,19 @@ public function setCounter()
 
     /**
      * @param array $arguments
-     *
-     * @return array
      */
-    public function suggestQuery($arguments)
+    public function suggestQuery($arguments): array
     {
-        $this->query = $this->getConnection()->createSuggester();
+        $query = $this->getConnection()->createSuggester();
         $results = [];
         if (array_key_exists('q', $arguments)) {
-            $this->query->setQuery($arguments['q']);
+            $query->setQuery($arguments['q']);
             if ($arguments['dictionary']) {
-                $this->query->setDictionary($arguments['dictionary']);
+                $query->setDictionary($arguments['dictionary']);
             }
 
             $this->addFacetFilters($arguments);
-            $solrResults = $this->getConnection()->execute($this->query)->getResults();
+            $solrResults = $this->getConnection()->execute($query)->getResults();
             foreach ($solrResults as $suggestions) {
                 $results = array_merge($results, $suggestions->getSuggestions());
             }
@@ -271,7 +261,7 @@ public function suggestQuery($arguments)
         return $results;
     }
 
-    protected function addEDisMax()
+    protected function addEDisMax(): void
     {
         $this->query->getEDisMax();
     }
@@ -280,10 +270,8 @@ protected function addEDisMax()
      * Adds filter queries for active facets to $query.
      *
      * @param array $arguments request arguments
-     *
-     * @return array
      */
-    protected function addFacetFilters($arguments)
+    protected function addFacetFilters(array $arguments): array
     {
         $activeFacets = $this->getActiveFacets($arguments);
         $activeFacetsForTemplate = [];
@@ -297,8 +285,9 @@ protected function addFacetFilters($arguments)
                     // records instead of the joined ones.
                     $queryString = $this->query->getQuery();
                     if ($queryString) {
-                        $queryString = $queryString.' '.Query::QUERY_OPERATOR_AND.' ';
+                        $queryString .= ' '.Query::QUERY_OPERATOR_AND.' ';
                     }
+
                     $queryString .= $facetQuery;
                     $this->query->setQuery($queryString);
                 } else {
@@ -315,6 +304,7 @@ protected function addFacetFilters($arguments)
                     $this->query->createFilterQuery($queryInfo)
                         ->setQuery($facetQuery);
                 }
+
                 $activeFacetsForTemplate[$facetID][$facetTerm] = $facetInfo;
             }
         }
@@ -327,7 +317,7 @@ protected function addFacetFilters($arguments)
      * Provides the facet setup enriched with the default values when no configuration
      * is present in the »facets« template variable.
      */
-    protected function addFacetQueries()
+    protected function addFacetQueries(): void
     {
         $facetConfiguration = $this->settings['facets'];
 
@@ -356,17 +346,17 @@ protected function addFacetQueries()
                                 );
                             }
                         }
+
+                        if (1 === (int) $facet['excludeOwnFilter']) {
+                            $queryForFacet->addExclude($this->tagForFacet($facetID));
+                        }
                     } else {
                         $queryForFacet = $facetSet->createFacetField($facetID);
-                        $queryForFacet->setField($facet['field'] ? $facet['field'] : $facetID)
+                        $queryForFacet->setField($facet['field'] ?: $facetID)
                             ->setMinCount($facet['fetchMinimum'])
                             ->setLimit($facet['fetchMaximum'])
                             ->setSort($facet['sortOrder']);
                     }
-
-                    if (1 == $facet['excludeOwnFilter']) {
-                        $queryForFacet->addExclude($this->tagForFacet($facetID));
-                    }
                 } else {
                     $this->logger->warning(sprintf('TypoScript facet %s does not have the required key »id«. Ignoring this facet.', $key),
                         [
@@ -381,7 +371,7 @@ protected function addFacetQueries()
         $this->setConfigurationValue('facets', $facetConfiguration);
     }
 
-    protected function addFeatures()
+    protected function addFeatures(): void
     {
         if ($this->settings['features']['eDisMax']) {
             $this->addEDisMax();
@@ -396,7 +386,7 @@ protected function addFeatures()
      *
      * @param array $arguments request arguments
      */
-    protected function addHighlighting($arguments)
+    protected function addHighlighting(array $arguments): void
     {
         $highlightConfig = SettingsUtility::getMergedSettings('highlight', $this->settings);
 
@@ -435,6 +425,7 @@ protected function addHighlighting($arguments)
                                         $queryTerm = $this->query->getHelper()->escapeTerm($queryTerm);
                                     }
                                 }
+
                                 $queryWords[] = $queryTerm;
                             }
                         }
@@ -455,6 +446,7 @@ protected function addHighlighting($arguments)
                 foreach ($queryWords as $queryWord) {
                     $queryComponents[] = '('.sprintf($highlightConfig['query'], $queryWord).')';
                 }
+
                 $queryString = implode(' OR ', $queryComponents);
 
                 $highlight->setQuery($queryString);
@@ -463,14 +455,16 @@ protected function addHighlighting($arguments)
             // Configure highlight fields.
             $highlight->addFields(implode(',', $highlightConfig['fields']));
 
-            // Configure the fragement length.
-            $highlight->setFragSize($highlightConfig['fragsize']);
+            // Configure the fragment length.
+            $highlight->setFragSize((int) $highlightConfig['fragsize']);
 
             // Set up alternative fields.
             if ($highlightConfig['alternateFields']) {
                 foreach ($highlightConfig['alternateFields'] as $fieldName => $alternateFieldName) {
                     $highlightField = $highlight->getField($fieldName);
-                    $highlightField->setAlternateField($alternateFieldName);
+                    if (null !== $highlightField) {
+                        $highlightField->setAlternateField($alternateFieldName);
+                    }
                 }
             }
 
@@ -492,7 +486,7 @@ protected function addHighlighting($arguments)
      *
      * @param array $arguments request arguments
      */
-    protected function addResultCountOptionsToTemplate($arguments)
+    protected function addResultCountOptionsToTemplate(array $arguments): void
     {
         $resultCountOptions = ['menu' => []];
 
@@ -525,7 +519,7 @@ protected function addResultCountOptionsToTemplate($arguments)
      *
      * @param array $arguments request arguments
      */
-    protected function addSortOrdersToTemplate($arguments)
+    protected function addSortOrdersToTemplate(array $arguments): void
     {
         $sortOptions = ['menu' => []];
 
@@ -541,6 +535,7 @@ protected function addSortOrdersToTemplate($arguments)
                     if (!$localisedLabel) {
                         $localisedLabel = $sortOption['id'];
                     }
+
                     $sortOptions['menu'][$sortOption['sortCriteria']] = $localisedLabel;
 
                     if ('default' === $sortOption['id']) {
@@ -569,10 +564,8 @@ protected function addSortOrdersToTemplate($arguments)
      * Checks that $sortString is well-formatted and adds the sort conidition
      * defined by it to $query.
      * Adds feedback about invalid sort string format to the page.
-     *
-     * @param string $sortString
      */
-    protected function addSortStringForQuery($sortString)
+    protected function addSortStringForQuery(string $sortString): void
     {
         if (!empty($sortString)) {
             $sortCriteria = explode(',', $sortString);
@@ -582,11 +575,9 @@ protected function addSortStringForQuery($sortString)
                     $sortDirection = Query::SORT_ASC;
                     if ('desc' === $sortCriterionParts[1]) {
                         $sortDirection = Query::SORT_DESC;
-                    } else {
-                        if ('asc' !== $sortCriterionParts[1]) {
-                            $this->logger->warning(sprintf('sort criterion »%s«’s sort direction is »%s« It should be »asc« or »desc«. Ignoring it.', $sortCriterion, $sortCriterionParts[1]));
-                            continue;
-                        }
+                    } elseif ('asc' !== $sortCriterionParts[1]) {
+                        $this->logger->warning(sprintf('sort criterion »%s«’s sort direction is »%s« It should be »asc« or »desc«. Ignoring it.', $sortCriterion, $sortCriterionParts[1]));
+                        continue;
                     }
 
                     $this->query->addSort($sortCriterionParts[0], $sortDirection);
@@ -602,7 +593,7 @@ protected function addSortStringForQuery($sortString)
      *
      * @return $this
      */
-    protected function addTypoScriptFilters()
+    protected function addTypoScriptFilters(): SolrServiceProvider
     {
         if (!empty($this->settings['additionalFilters'])) {
             foreach ($this->settings['additionalFilters'] as $key => $filterQuery) {
@@ -616,20 +607,16 @@ protected function addTypoScriptFilters()
 
     /**
      * Returns the number of the last result on the page.
-     *
-     * @return int
      */
-    protected function counterEnd()
+    protected function counterEnd(): int
     {
         return $this->getOffset() + $this->getCount();
     }
 
     /**
      * Returns the number of the first result on the page.
-     *
-     * @return int
      */
-    protected function counterStart()
+    protected function counterStart(): int
     {
         return $this->getOffset() + 1;
     }
@@ -637,7 +624,7 @@ protected function counterStart()
     /**
      * Creates a blank query, sets up TypoScript filters and adds it to the view.
      */
-    protected function createQuery()
+    protected function createQuery(): void
     {
         $this->query = $this->connection->createSelect();
         $this->addFeatures();
@@ -651,7 +638,7 @@ protected function createQuery()
      *
      * @param array $arguments request arguments
      */
-    protected function createQueryForArguments($arguments)
+    protected function createQueryForArguments(array $arguments): void
     {
         $this->createQuery();
 
@@ -665,7 +652,7 @@ protected function createQueryForArguments($arguments)
         $queryParameters = [];
         if (is_array($rawQueryParameters) && [] !== $rawQueryParameters) {
             foreach ($rawQueryParameters as $key => $value) {
-                if (is_array($value) && count(array_filter($value)) > 0) {
+                if (is_array($value) && [] !== array_filter($value)) {
                     $queryParameters[$key] = array_filter($value);
                 } elseif (!empty($value) && !is_array($value)) {
                     $queryParameters[$key] = $value;
@@ -693,7 +680,7 @@ protected function createQueryForArguments($arguments)
     /**
      * @return string
      */
-    protected function getAction()
+    protected function getAction(): ?string
     {
         return $this->action;
     }
@@ -705,7 +692,7 @@ protected function getAction()
      *
      * @return array of arrays with information about active facets
      */
-    protected function getActiveFacets($arguments)
+    protected function getActiveFacets(array $arguments): array
     {
         $activeFacets = [];
 
@@ -726,10 +713,7 @@ protected function getActiveFacets($arguments)
         return $activeFacets;
     }
 
-    /**
-     * @return Client
-     */
-    protected function getConnection()
+    protected function getConnection(): Client
     {
         return $this->connection;
     }
@@ -737,7 +721,7 @@ protected function getConnection()
     /**
      * @return string
      */
-    protected function getControllerExtensionKey()
+    protected function getControllerExtensionKey(): ?string
     {
         return $this->controllerExtensionKey;
     }
@@ -748,11 +732,9 @@ protected function getControllerExtensionKey()
      * * TypoScript setting »paging.perPage«
      * limited by the setting »paging.maximumPerPage«.
      *
-     * @param array $arguments overrides $this->requestArguments if set
-     *
-     * @return int
+     * @param array|null $arguments overrides $this->requestArguments if set
      */
-    protected function getCount($arguments = null)
+    protected function getCount(?array $arguments = null): int
     {
         if (null === $arguments) {
             $arguments = $this->getRequestArguments();
@@ -775,20 +757,16 @@ protected function getCount($arguments = null)
     /**
      * Returns the facet configuration for the given $id.
      *
-     * @param string $id
-     *
      * @return array
      */
-    protected function getFacetConfig($id)
+    protected function getFacetConfig(string $id): ?array
     {
         $config = null;
 
         foreach ($this->settings['facets'] as $facet) {
-            if (array_key_exists('id', $facet)) {
-                if ($facet['id'] === $id) {
-                    $config = $facet;
-                    break;
-                }
+            if (array_key_exists('id', $facet) && $facet['id'] === $id) {
+                $config = $facet;
+                break;
             }
         }
 
@@ -799,16 +777,13 @@ protected function getFacetConfig($id)
      * Returns query for the given facet $ID and $term based on the facet’s
      * configuration.
      *
-     * @param array  $facetConfig
-     * @param string $queryTerm
-     *
      * @return string query string
      */
-    protected function getFacetQuery($facetConfig, $queryTerm)
+    protected function getFacetQuery(array $facetConfig, string $queryTerm): ?string
     {
         $queryString = null;
 
-        if ($facetConfig) {
+        if ([] !== $facetConfig) {
             if (array_key_exists('facetQuery', $facetConfig)) {
                 // Facet queries are configured: use one of them.
                 foreach ($facetConfig['facetQuery'] as $facetQueryConfig) {
@@ -817,6 +792,7 @@ protected function getFacetQuery($facetConfig, $queryTerm)
                         break;
                     }
                 }
+
                 if (null === $queryString) {
                     $this->logger->info(sprintf('Results for Facet »%s« with facetQuery ID »%s« were requested, but this facetQuery is not configured. Building a generic facet query instead.', $facetConfig['id'], $queryTerm),
                         [
@@ -833,12 +809,12 @@ protected function getFacetQuery($facetConfig, $queryTerm)
                 if (array_key_exists('query', $facetConfig)) {
                     $queryPattern = $facetConfig['query'];
                 } else {
-                    $queryPattern = ($facetConfig['field'] ? $facetConfig['field'] : $facetConfig['id']).':'.'%s';
+                    $queryPattern = ($facetConfig['field'] ?: $facetConfig['id']).':'.'%s';
                 }
 
                 // Hack: convert strings »RANGE XX TO YY« Solr style range queries »[XX TO YY]«
                 // (because PHP loses ] in array keys during URL parsing)
-                $queryTerm = preg_replace('/RANGE (.*) TO (.*)/', '[\1 TO \2]', $queryTerm);
+                $queryTerm = preg_replace('#RANGE (.*) TO (.*)#', '[\1 TO \2]', $queryTerm);
                 $queryString = sprintf($queryPattern, $queryTerm);
             }
         } else {
@@ -853,11 +829,9 @@ protected function getFacetQuery($facetConfig, $queryTerm)
     /**
      * Returns the index of the first row to return.
      *
-     * @param array $arguments overrides $this->requestArguments if set
-     *
-     * @return int
+     * @param array|null $arguments overrides $this->requestArguments if set
      */
-    protected function getOffset($arguments = null)
+    protected function getOffset(?array $arguments = null): int
     {
         if (null === $arguments) {
             $arguments = $this->requestArguments;
@@ -867,10 +841,8 @@ protected function getOffset($arguments = null)
 
         if (array_key_exists('start', $arguments)) {
             $offset = (int) $arguments['start'];
-        } else {
-            if (array_key_exists('page', $arguments)) {
-                $offset = ((int) $arguments['page'] - 1) * $this->getCount();
-            }
+        } elseif (array_key_exists('page', $arguments)) {
+            $offset = ((int) $arguments['page'] - 1) * $this->getCount();
         }
 
         $this->setConfigurationValue('offset', $offset);
@@ -879,13 +851,10 @@ protected function getOffset($arguments = null)
     }
 
     /**
-     * @param $assignments
      * @param $id
      * @param $arguments
-     *
-     * @return mixed
      */
-    protected function getRecordsWithUnderlyingQuery(array $assignments, array $index, $id, $arguments)
+    protected function getRecordsWithUnderlyingQuery(array $assignments, array $index, $id, $arguments): array
     {
         $connection = $this->getConnection();
 
@@ -905,6 +874,7 @@ protected function getRecordsWithUnderlyingQuery(array $assignments, array $inde
                         $assignments['document-previous'] = $resultSet[0];
                         $assignments['document-previous-number'] = $index['previousIndex'] + 1;
                     }
+
                     $nextResultIndex = 1 + $index['resultIndexOffset'];
                     if (count($resultSet) > $nextResultIndex) {
                         $assignments['document-next'] = $resultSet[$nextResultIndex];
@@ -918,11 +888,11 @@ protected function getRecordsWithUnderlyingQuery(array $assignments, array $inde
             } else {
                 $this->logger->error('»detail« action query with underlying query returned no results.', ['arguments' => $arguments]);
             }
-        } catch (HttpException $exception) {
+        } catch (HttpException $httpException) {
             $this->logger->error('Solr Exception (Timeout?)',
                 [
                     'arguments' => $arguments,
-                    'exception' => LoggerUtility::exceptionToArray($exception),
+                    'exception' => LoggerUtility::exceptionToArray($httpException),
                 ]
             );
         }
@@ -954,11 +924,11 @@ protected function getTheRecordSpecified($id, $assignments)
             } else {
                 $this->logger->error(sprintf('»detail« action query for id »%d« returned no results.', $id), ['arguments' => $this->getRequestArguments()]);
             }
-        } catch (HttpException $exception) {
+        } catch (HttpException $httpException) {
             $this->logger->error('Solr Exception (Timeout?)',
                 [
                     'arguments' => $this->getRequestArguments(),
-                    'exception' => LoggerUtility::exceptionToArray($exception),
+                    'exception' => LoggerUtility::exceptionToArray($httpException),
                 ]
             );
         }
@@ -970,12 +940,8 @@ protected function getTheRecordSpecified($id, $assignments)
      * Takes the array of search query parameters and builds an array of Solr
      * search strings from it, using the »queryFields« configuration from TypoScript.
      * These search strings need to be ANDed together for the complete query.
-     *
-     * @param array $queryParameters
-     *
-     * @return array
      */
-    protected function queryComponentsForQueryParameters($queryParameters)
+    protected function queryComponentsForQueryParameters(array $queryParameters): array
     {
         $queryComponents = [];
 
@@ -1009,6 +975,7 @@ protected function queryComponentsForQueryParameters($queryParameters)
                     if (!is_array($defaults)) {
                         $defaults = [$defaults];
                     }
+
                     foreach ($defaults as $defaultKey => $default) {
                         if (!array_key_exists($defaultKey, $queryTerms)) {
                             $queryTerms[$defaultKey] = $default;
@@ -1027,6 +994,7 @@ protected function queryComponentsForQueryParameters($queryParameters)
                                 $escapedQueryTerms[$key] = $this->query->getHelper()->escapeTerm($term);
                             }
                         }
+
                         $queryTerms = $escapedQueryTerms;
                     }
                 }
@@ -1035,11 +1003,10 @@ protected function queryComponentsForQueryParameters($queryParameters)
                 $queryFormat = '';
                 if (!$queryAlternate) {
                     $queryFormat = $fieldInfo['query'];
-                } else {
-                    if (array_key_exists($queryAlternate, $fieldInfo['queryAlternate'])) {
-                        $queryFormat = $fieldInfo['queryAlternate'][$queryAlternate];
-                    }
+                } elseif (array_key_exists($queryAlternate, $fieldInfo['queryAlternate'])) {
+                    $queryFormat = $fieldInfo['queryAlternate'][$queryAlternate];
                 }
+
                 if (empty($queryFormat)) {
                     $queryFormat = $fieldID.':%s';
                 }
@@ -1048,7 +1015,7 @@ protected function queryComponentsForQueryParameters($queryParameters)
 
                 $magicFieldPrefix = '';
 
-                if ( (array_key_exists('luceneMatchVersionNumber', $this->settings) && (int) $this->settings['luceneMatchVersionNumber'] < 8) || (!array_key_exists('luceneMatchVersionNumber', $this->settings)) ) {
+                if ((array_key_exists('luceneMatchVersionNumber', $this->settings) && (int) $this->settings['luceneMatchVersionNumber'] < 8) || (!array_key_exists('luceneMatchVersionNumber', $this->settings))) {
                     $magicFieldPrefix = '_query_:';
                 }
 
@@ -1059,14 +1026,14 @@ protected function queryComponentsForQueryParameters($queryParameters)
                     $queryPart = $magicFieldPrefix.$this->query->getHelper()->escapePhrase(vsprintf($queryFormat, $queryTerms));
                 }
 
-                if ($queryPart) {
+                if ('' !== $queryPart && '0' !== $queryPart) {
                     $queryComponents[$fieldID] = $queryPart;
                 }
             }
         }
 
         // Ask for all results if there is no query.
-        if (0 === count($queryComponents)) {
+        if ([] === $queryComponents) {
             $queryComponents[] = $this->settings['defaultQuery'];
         }
 
@@ -1076,15 +1043,14 @@ protected function queryComponentsForQueryParameters($queryParameters)
     /**
      * Adds information about the selected items for a given facet to $activeFacets.
      *
-     * @param array  $activeFacets
      * @param string $facetID        ID of the facet to set
      * @param array  $facetSelection array of selected items for the facet
      */
-    protected function setActiveFacetSelectionForID(&$activeFacets, $facetID, $facetSelection)
+    protected function setActiveFacetSelectionForID(array &$activeFacets, string $facetID, array $facetSelection): void
     {
         $facetQueries = [];
         $facetConfig = $this->getFacetConfig($facetID);
-        foreach ($facetSelection as $facetTerm => $facetStatus) {
+        foreach (array_keys($facetSelection) as $facetTerm) {
             $facetInfo = [
                 'id' => $facetID,
                 'config' => $facetConfig,
@@ -1093,7 +1059,8 @@ protected function setActiveFacetSelectionForID(&$activeFacets, $facetID, $facet
             ];
             $facetQueries[$facetTerm] = $facetInfo;
         }
-        if (count($facetQueries) > 0) {
+
+        if ([] !== $facetQueries) {
             $activeFacets[$facetID] = $facetQueries;
         }
     }
@@ -1101,7 +1068,7 @@ protected function setActiveFacetSelectionForID(&$activeFacets, $facetID, $facet
     /**
      * @param mixed $connection
      */
-    protected function setConnection($connection)
+    protected function setConnection($connection): void
     {
         $this->connection = $connection;
     }
@@ -1111,7 +1078,7 @@ protected function setConnection($connection)
      *
      * @param array $arguments request arguments
      */
-    protected function setFields($arguments)
+    protected function setFields(array $arguments): void
     {
         $fieldsConfig = SettingsUtility::getMergedSettings('dataFields', $this->settings, $this->getAction());
         $fields = [];
@@ -1119,10 +1086,8 @@ protected function setFields($arguments)
         // Use field list from query parameters or from defaults.
         if (array_key_exists('data-fields', $arguments) && $arguments['data-fields']) {
             $fields = explode(',', $arguments['data-fields']);
-        } else {
-            if ($fieldsConfig['default']) {
-                $fields = array_values($fieldsConfig['default']);
-            }
+        } elseif ($fieldsConfig['default']) {
+            $fields = array_values($fieldsConfig['default']);
         }
 
         // If allowed fields are configured, keep only those.
@@ -1138,7 +1103,7 @@ protected function setFields($arguments)
         }
 
         // Only set fields of the query if there is a result. Otherwise use the default setting.
-        if ($fields) {
+        if ([] !== $fields) {
             $this->query->setFields($fields);
         }
     }
@@ -1148,7 +1113,7 @@ protected function setFields($arguments)
      *
      * @param array $arguments request arguments
      */
-    protected function setRange($arguments)
+    protected function setRange(array $arguments): void
     {
         $this->query->setStart($this->getOffset($arguments));
         $this->query->setRows($this->getCount($arguments));
@@ -1159,18 +1124,16 @@ protected function setRange($arguments)
      *
      * @param array $arguments request arguments
      */
-    protected function setSortOrder($arguments)
+    protected function setSortOrder(array $arguments): void
     {
         $sortString = '';
         if (!empty($arguments['sort'])) {
             $sortString = $arguments['sort'];
-        } else {
-            if (!empty($this->settings['sort'])) {
-                foreach ($this->settings['sort'] as $sortSetting) {
-                    if ('default' === $sortSetting['id']) {
-                        $sortString = $sortSetting['sortCriteria'];
-                        break;
-                    }
+        } elseif (!empty($this->settings['sort'])) {
+            foreach ($this->settings['sort'] as $sortSetting) {
+                if ('default' === $sortSetting['id']) {
+                    $sortString = $sortSetting['sortCriteria'];
+                    break;
                 }
             }
         }
@@ -1181,12 +1144,8 @@ protected function setSortOrder($arguments)
 
     /**
      * Returns the facet/filter key for the given $facetID.
-     *
-     * @param string $facetID
-     *
-     * @return string
      */
-    protected function tagForFacet($facetID)
+    protected function tagForFacet(string $facetID): string
     {
         return 'facet-'.$facetID;
     }
diff --git a/Classes/Utility/FrontendUtility.php b/Classes/Utility/FrontendUtility.php
index 2852b234..20a33fac 100644
--- a/Classes/Utility/FrontendUtility.php
+++ b/Classes/Utility/FrontendUtility.php
@@ -56,15 +56,19 @@ public static function addQueryInformationAsJavaScript($query, array $settings,
             if (array_key_exists('facet', $arguments)) {
                 $underlyingQuery['facet'] = $arguments['facet'];
             }
+
             if (null !== $position) {
                 $underlyingQuery['position'] = $position;
             }
+
             if ($arguments['count']) {
                 $underlyingQuery['count'] = $arguments['count'];
             }
+
             if ($arguments['sort']) {
                 $underlyingQuery['sort'] = $arguments['sort'];
             }
+
             $scriptTag->setContent('var underlyingQuery = '.json_encode($underlyingQuery).';');
 
             return $scriptTag->render();
@@ -80,13 +84,6 @@ public static function addQueryInformationAsJavaScript($query, array $settings,
      */
     public static function getIndexes($underlyingQueryInfo)
     {
-        // These indexes are 0-based for Solr & PHP. The user visible numbering is 1-based.
-        $index = [];
-        $index['positionIndex'] = $underlyingQueryInfo['position'] - 1;
-        $index['previousIndex'] = max([$index['positionIndex'] - 1, 0]);
-        $index['nextIndex'] = $index['positionIndex'] + 1;
-        $index['resultIndexOffset'] = (0 === $index['positionIndex']) ? 0 : 1;
-
-        return $index;
+        return ['positionIndex' => $underlyingQueryInfo['position'] - 1, 'previousIndex' => max([$index['positionIndex'] - 1, 0]), 'nextIndex' => $index['positionIndex'] + 1, 'resultIndexOffset' => (0 === $index['positionIndex']) ? 0 : 1];
     }
 }
diff --git a/Classes/Utility/UpgradeUtility.php b/Classes/Utility/UpgradeUtility.php
new file mode 100644
index 00000000..c9813c72
--- /dev/null
+++ b/Classes/Utility/UpgradeUtility.php
@@ -0,0 +1,21 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Subugoe\Find\Utility;
+
+class UpgradeUtility
+{
+    public static function handleSolariumUpgrade(array $connectionSettings): array
+    {
+        trigger_error('Please read the upgrading instructions at https://github.com/subugoe/typo3-find/blob/main/UPGRADING.md', E_USER_DEPRECATED);
+
+        if (false !== strpos($connectionSettings['path'], '/solr/')) {
+            $connectionSettings['core'] = str_replace('/solr/', '', $connectionSettings['path']);
+            $connectionSettings['core'] = str_replace('/', '', $connectionSettings['core']);
+            $connectionSettings['path'] = '/';
+        }
+
+        return $connectionSettings;
+    }
+}
diff --git a/Classes/ViewHelpers/Data/ArrayFirstViewHelper.php b/Classes/ViewHelpers/Data/ArrayFirstViewHelper.php
index 77e1f81f..b75ebbe4 100644
--- a/Classes/ViewHelpers/Data/ArrayFirstViewHelper.php
+++ b/Classes/ViewHelpers/Data/ArrayFirstViewHelper.php
@@ -59,7 +59,7 @@ public static function renderStatic(array $arguments, \Closure $renderChildrenCl
             $array = $renderChildrenClosure();
         }
 
-        if (is_array($array) && count($array) > 0) {
+        if (is_array($array) && [] !== $array) {
             $arrayKeys = array_keys($array);
             $firstKey = $arrayKeys[0];
             $result = $array[$firstKey];
diff --git a/Classes/ViewHelpers/Data/NewArrayViewHelper.php b/Classes/ViewHelpers/Data/NewArrayViewHelper.php
index 3073cb7b..94f5ed68 100644
--- a/Classes/ViewHelpers/Data/NewArrayViewHelper.php
+++ b/Classes/ViewHelpers/Data/NewArrayViewHelper.php
@@ -86,6 +86,7 @@ public static function renderStatic(array $arguments, \Closure $renderChildrenCl
             if ($renderingContext->getVariableProvider()->exists($variableName)) {
                 $renderingContext->getVariableProvider()->remove($variableName);
             }
+
             $renderingContext->getVariableProvider()->add($variableName, $result);
             $result = $renderChildrenClosure();
             if (true !== $arguments['global']) {
diff --git a/Classes/ViewHelpers/Data/SplitViewHelper.php b/Classes/ViewHelpers/Data/SplitViewHelper.php
index cfaba07f..28c73779 100644
--- a/Classes/ViewHelpers/Data/SplitViewHelper.php
+++ b/Classes/ViewHelpers/Data/SplitViewHelper.php
@@ -37,7 +37,10 @@
  */
 class SplitViewHelper extends AbstractViewHelper
 {
-    const DEFAULT_SEPARATOR = ', ';
+    /**
+     * @var string
+     */
+    public const DEFAULT_SEPARATOR = ', ';
 
     /**
      * Register arguments.
diff --git a/Classes/ViewHelpers/Data/TransposeViewHelper.php b/Classes/ViewHelpers/Data/TransposeViewHelper.php
index 9abe14f6..f48ca253 100644
--- a/Classes/ViewHelpers/Data/TransposeViewHelper.php
+++ b/Classes/ViewHelpers/Data/TransposeViewHelper.php
@@ -70,6 +70,7 @@ public static function renderStatic(
                 foreach ($arrays as $key => $array) {
                     $row[$key] = $array[$rowIndex];
                 }
+
                 $rows[] = $row;
             }
 
@@ -105,11 +106,9 @@ protected static function identicalLengths($arrays)
         foreach ($arrays as $array) {
             if (null === $length) {
                 $length = count($array);
-            } else {
-                if ($length !== count($array)) {
-                    $result = false;
-                    break;
-                }
+            } elseif ($length !== count($array)) {
+                $result = false;
+                break;
             }
         }
 
diff --git a/Classes/ViewHelpers/Data/ValueForKeyViewHelper.php b/Classes/ViewHelpers/Data/ValueForKeyViewHelper.php
index a8fe26d2..df70a041 100644
--- a/Classes/ViewHelpers/Data/ValueForKeyViewHelper.php
+++ b/Classes/ViewHelpers/Data/ValueForKeyViewHelper.php
@@ -54,10 +54,8 @@ public static function renderStatic(
     ) {
         $result = null;
 
-        if ($arguments['array']) {
-            if (array_key_exists($arguments['key'], $arguments['array'])) {
-                $result = $arguments['array'][$arguments['key']];
-            }
+        if ($arguments['array'] && array_key_exists($arguments['key'], $arguments['array'])) {
+            $result = $arguments['array'][$arguments['key']];
         }
 
         return $result;
diff --git a/Classes/ViewHelpers/Find/FacetLinkArgumentsViewHelper.php b/Classes/ViewHelpers/Find/FacetLinkArgumentsViewHelper.php
index e009c892..ad6dda1b 100644
--- a/Classes/ViewHelpers/Find/FacetLinkArgumentsViewHelper.php
+++ b/Classes/ViewHelpers/Find/FacetLinkArgumentsViewHelper.php
@@ -84,8 +84,10 @@ public static function renderStatic(
                 if (array_key_exists($facetTerm, $activeFacets[$facetID])) {
                     $itemToRemove .= '['.$facetTerm.']';
                 }
+
                 $result[] = $itemToRemove;
             }
+
             // Go back to page 1.
             $result[] = 'tx_find_find[page]';
         } elseif ('add' === $mode) {
diff --git a/Classes/ViewHelpers/Find/HighlightFieldViewHelper.php b/Classes/ViewHelpers/Find/HighlightFieldViewHelper.php
index 34045a73..41f8deb9 100644
--- a/Classes/ViewHelpers/Find/HighlightFieldViewHelper.php
+++ b/Classes/ViewHelpers/Find/HighlightFieldViewHelper.php
@@ -51,8 +51,8 @@ class HighlightFieldViewHelper extends AbstractViewHelper
     public function initializeArguments()
     {
         parent::initializeArguments();
-        $this->registerArgument('results', '\Solarium\QueryType\Select\Result\Result', 'Query results', true);
-        $this->registerArgument('document', '\Solarium\QueryType\Select\Result\Document', 'Result document to work on',
+        $this->registerArgument('results', \Solarium\QueryType\Select\Result\Result::class, 'Query results', true);
+        $this->registerArgument('document', \Solarium\QueryType\Select\Result\Document::class, 'Result document to work on',
             true);
         $this->registerArgument('field', 'string', 'name of field in document to highlight', true);
         $this->registerArgument('alternateField', 'string',
@@ -175,11 +175,7 @@ protected static function highlightSingleField($fieldString, $highlightInfo, $ar
 
         // If no highlighted string is present, use the original one.
         if (null === $result) {
-            if ($arguments['raw']) {
-                $result = $fieldString;
-            } else {
-                $result = htmlspecialchars($fieldString);
-            }
+            $result = $arguments['raw'] ? $fieldString : htmlspecialchars($fieldString);
         }
 
         return $result;
diff --git a/Classes/ViewHelpers/Find/LocalizedFacetDataViewHelper.php b/Classes/ViewHelpers/Find/LocalizedFacetDataViewHelper.php
index 10368fb9..448ea0cd 100644
--- a/Classes/ViewHelpers/Find/LocalizedFacetDataViewHelper.php
+++ b/Classes/ViewHelpers/Find/LocalizedFacetDataViewHelper.php
@@ -91,7 +91,8 @@ public static function renderStatic(
                     $localizationsForFacet[$facetEntryID] = $localizedFacetEntryName;
                 }
             }
-            if (count($localizationsForFacet) > 0) {
+
+            if ([] !== $localizationsForFacet) {
                 $facetEntryNames[$facetID] = $localizationsForFacet;
             }
         }
diff --git a/Classes/ViewHelpers/Find/PageListViewHelper.php b/Classes/ViewHelpers/Find/PageListViewHelper.php
index 526cb0a8..6cd3a58d 100644
--- a/Classes/ViewHelpers/Find/PageListViewHelper.php
+++ b/Classes/ViewHelpers/Find/PageListViewHelper.php
@@ -69,33 +69,24 @@ public static function renderStatic(
             if ($pageIndex === $currentPage) {
                 $pageInfo['status'] = 'current';
                 $pageInfo['current'] = true;
+            } elseif ((1 === $pageIndex | $pageIndex === $numberOfPages) !== 0) {
+                $pageInfo['status'] = 'edge';
+            } elseif (abs($pageIndex - $currentPage) <= $adjacentPages) {
+                $pageInfo['status'] = 'adjacent';
+            } elseif (($pageIndex < $adjacentFirst && $adjacentFirst <= 1 + $minimumGapSize)
+                || ($pageIndex > $adjacentLast && $numberOfPages - $adjacentLast <= $minimumGapSize)) {
+                $pageInfo['status'] = 'gapfiller';
             } else {
-                if (1 === $pageIndex | $pageIndex === $numberOfPages) {
-                    $pageInfo['status'] = 'edge';
-                } else {
-                    if (abs($pageIndex - $currentPage) <= $adjacentPages) {
-                        $pageInfo['status'] = 'adjacent';
-                    } else {
-                        if (($pageIndex < $adjacentFirst && $adjacentFirst <= 1 + $minimumGapSize)
-                            || ($pageIndex > $adjacentLast && $numberOfPages - $adjacentLast <= $minimumGapSize)
-                        ) {
-                            $pageInfo['status'] = 'gapfiller';
-                        } else {
-                            $pageInfo['status'] = 'gap';
-                            $pageInfo['gap'] = true;
-                        }
-                    }
-                }
+                $pageInfo['status'] = 'gap';
+                $pageInfo['gap'] = true;
             }
 
             if ('gap' === $pageInfo['status']) {
                 $pageInfo['text'] = '…';
                 if ($pageIndex < $currentPage) {
                     $pageIndex = $currentPage - $adjacentPages;
-                } else {
-                    if ($pageIndex > $currentPage) {
-                        $pageIndex = $numberOfPages;
-                    }
+                } elseif ($pageIndex > $currentPage) {
+                    $pageIndex = $numberOfPages;
                 }
             } else {
                 $pageInfo['text'] = (string) $pageIndex;
diff --git a/Classes/ViewHelpers/Find/PageNumberForResultNumberViewHelper.php b/Classes/ViewHelpers/Find/PageNumberForResultNumberViewHelper.php
index b004d19d..76353473 100644
--- a/Classes/ViewHelpers/Find/PageNumberForResultNumberViewHelper.php
+++ b/Classes/ViewHelpers/Find/PageNumberForResultNumberViewHelper.php
@@ -39,8 +39,10 @@ class PageNumberForResultNumberViewHelper extends AbstractViewHelper
 {
     /**
      * Avoid divisions by zero.
+     *
+     * @var int
      */
-    const DEFAULT_RESULTS_PER_PAGE = 20;
+    public const DEFAULT_RESULTS_PER_PAGE = 20;
 
     /**
      * Registers own arguments.
@@ -64,8 +66,6 @@ public static function renderStatic(
             $arguments['resultsPerPage'] = self::DEFAULT_RESULTS_PER_PAGE;
         }
 
-        $pageNumber = (int) ceil($arguments['resultNumber'] / $arguments['resultsPerPage']);
-
-        return $pageNumber;
+        return (int) ceil($arguments['resultNumber'] / $arguments['resultsPerPage']);
     }
 }
diff --git a/Classes/ViewHelpers/Find/SelectOptionsForFacetViewHelper.php b/Classes/ViewHelpers/Find/SelectOptionsForFacetViewHelper.php
index 215a1b98..63573c81 100644
--- a/Classes/ViewHelpers/Find/SelectOptionsForFacetViewHelper.php
+++ b/Classes/ViewHelpers/Find/SelectOptionsForFacetViewHelper.php
@@ -95,6 +95,7 @@ public static function renderStatic(
                 $valueParts = explode($arguments['sortPrefixSeparator'], $value, 2);
                 $strippedResult[$key] = $valueParts[count($valueParts) - 1];
             }
+
             $result = $strippedResult;
         }
 
diff --git a/Classes/ViewHelpers/Format/RegexpViewHelper.php b/Classes/ViewHelpers/Format/RegexpViewHelper.php
index 94b477a5..a4a595a0 100644
--- a/Classes/ViewHelpers/Format/RegexpViewHelper.php
+++ b/Classes/ViewHelpers/Format/RegexpViewHelper.php
@@ -66,12 +66,10 @@ public static function renderStatic(
         $result = null;
         if (null === $arguments['replace']) {
             $result = preg_match($arguments['match'], $input);
+        } elseif (!$arguments['useMBEreg']) {
+            $result = preg_replace($arguments['match'], $arguments['replace'], $input);
         } else {
-            if (!$arguments['useMBEreg']) {
-                $result = preg_replace($arguments['match'], $arguments['replace'], $input);
-            } else {
-                $result = mb_ereg_replace($arguments['match'], $arguments['replace'], $input);
-            }
+            $result = mb_ereg_replace($arguments['match'], $arguments['replace'], $input);
         }
 
         return $result;
diff --git a/Classes/ViewHelpers/Format/SolrEscapeViewHelper.php b/Classes/ViewHelpers/Format/SolrEscapeViewHelper.php
index a1b972b0..086ed510 100644
--- a/Classes/ViewHelpers/Format/SolrEscapeViewHelper.php
+++ b/Classes/ViewHelpers/Format/SolrEscapeViewHelper.php
@@ -61,12 +61,6 @@ public static function renderStatic(
 
         $solariumHelper = new \Solarium\Core\Query\Helper();
 
-        if ($arguments['phrase']) {
-            $escapedString = $solariumHelper->escapePhrase($string);
-        } else {
-            $escapedString = $solariumHelper->escapeTerm($string);
-        }
-
-        return $escapedString;
+        return $arguments['phrase'] ? $solariumHelper->escapePhrase($string) : $solariumHelper->escapeTerm($string);
     }
 }
diff --git a/Classes/ViewHelpers/Format/StripViewHelper.php b/Classes/ViewHelpers/Format/StripViewHelper.php
index 74fb8188..9b794ef8 100644
--- a/Classes/ViewHelpers/Format/StripViewHelper.php
+++ b/Classes/ViewHelpers/Format/StripViewHelper.php
@@ -63,12 +63,6 @@ public static function renderStatic(
             $string = $renderChildrenClosure();
         }
 
-        if (null === $arguments['strip']) {
-            $string = trim($string);
-        } else {
-            $string = trim($string, $arguments['strip']);
-        }
-
-        return $string;
+        return null === $arguments['strip'] ? trim($string) : trim($string, $arguments['strip']);
     }
 }
diff --git a/Classes/ViewHelpers/Format/XMLViewHelper.php b/Classes/ViewHelpers/Format/XMLViewHelper.php
index db7043d6..38ac1831 100644
--- a/Classes/ViewHelpers/Format/XMLViewHelper.php
+++ b/Classes/ViewHelpers/Format/XMLViewHelper.php
@@ -59,14 +59,9 @@ public static function renderStatic(
         $XML->formatOutput = true;
         $XML->encoding = 'UTF-8';
         $XML->loadXML($input);
-        if ($arguments['htmloutput']) {
-            $result = $XML->saveHTML();
-        } else {
-            $result = $XML->saveXML();
-        }
 
         // TODO: Error handling?
 
-        return $result;
+        return $arguments['htmloutput'] ? $XML->saveHTML() : $XML->saveXML();
     }
 }
diff --git a/Classes/ViewHelpers/LinkedData/ContainerViewHelper.php b/Classes/ViewHelpers/LinkedData/ContainerViewHelper.php
index 268cdf3a..247c16aa 100644
--- a/Classes/ViewHelpers/LinkedData/ContainerViewHelper.php
+++ b/Classes/ViewHelpers/LinkedData/ContainerViewHelper.php
@@ -66,8 +66,7 @@ public static function renderStatic(
 
         $LDRenderer = Renderer\AbstractRenderer::instantiateSubclassForType($arguments['format']);
         $LDRenderer->setPrefixes($arguments['prefixes']);
-        $result = $LDRenderer->renderItems($items);
 
-        return $result;
+        return $LDRenderer->renderItems($items);
     }
 }
diff --git a/Classes/ViewHelpers/LinkedData/Renderer/AbstractRenderer.php b/Classes/ViewHelpers/LinkedData/Renderer/AbstractRenderer.php
index bc0124fa..ec0826b3 100644
--- a/Classes/ViewHelpers/LinkedData/Renderer/AbstractRenderer.php
+++ b/Classes/ViewHelpers/LinkedData/Renderer/AbstractRenderer.php
@@ -34,15 +34,9 @@
  */
 abstract class AbstractRenderer
 {
-    /**
-     * @var array
-     */
-    protected $prefixes = [];
+    protected array $prefixes = [];
 
-    /**
-     * @var array
-     */
-    protected $usedPrefixes = [];
+    protected array $usedPrefixes = [];
 
     /**
      * @param $type
@@ -53,12 +47,10 @@ public static function instantiateSubclassForType($type)
     {
         if ('rdf' === $type) {
             $instance = GeneralUtility::makeInstance(RDFRenderer::class);
+        } elseif ('json-ld' === $type) {
+            $instance = GeneralUtility::makeInstance(JSONLDRenderer::class);
         } else {
-            if ('json-ld' === $type) {
-                $instance = GeneralUtility::makeInstance(JSONLDRenderer::class);
-            } else {
-                $instance = GeneralUtility::makeInstance(TurtleRenderer::class);
-            }
+            $instance = GeneralUtility::makeInstance(TurtleRenderer::class);
         }
 
         return $instance;
diff --git a/Classes/ViewHelpers/LinkedData/Renderer/JSONLDRenderer.php b/Classes/ViewHelpers/LinkedData/Renderer/JSONLDRenderer.php
index 57be2173..1c78286c 100644
--- a/Classes/ViewHelpers/LinkedData/Renderer/JSONLDRenderer.php
+++ b/Classes/ViewHelpers/LinkedData/Renderer/JSONLDRenderer.php
@@ -57,6 +57,7 @@ public function renderItems($items)
                         if ($properties['language']) {
                             $object['@language'] = $properties['language'];
                         }
+
                         if ($properties['type']) {
                             $object['@type'] = $properties['type'];
                         }
@@ -104,11 +105,9 @@ protected function prefixedName($name)
                 $name = str_replace($URI, $acronym.':', $name);
                 $this->usedPrefixes[$acronym] = true;
                 break;
-            } else {
-                if (0 === strpos($name, $acronym.':')) {
-                    $this->usedPrefixes[$acronym] = true;
-                    break;
-                }
+            } elseif (0 === strpos($name, $acronym.':')) {
+                $this->usedPrefixes[$acronym] = true;
+                break;
             }
         }
 
diff --git a/Classes/ViewHelpers/LinkedData/Renderer/RDFRenderer.php b/Classes/ViewHelpers/LinkedData/Renderer/RDFRenderer.php
index 3de226f3..bfcd51a2 100644
--- a/Classes/ViewHelpers/LinkedData/Renderer/RDFRenderer.php
+++ b/Classes/ViewHelpers/LinkedData/Renderer/RDFRenderer.php
@@ -40,7 +40,7 @@ class RDFRenderer extends AbstractRenderer implements RendererInterface
      */
     public function renderItems($items)
     {
-        $doc = new \DomDocument();
+        $doc = new \DOMDocument();
         $this->prefixes['rdf'] = 'http://www.w3.org/1999/02/22-rdf-syntax-ns#';
         $rdf = $doc->createElement($this->prefixedName('rdf:RDF'));
         $doc->appendChild($rdf);
@@ -62,12 +62,14 @@ public function renderItems($items)
                         if ($this->prefixes[$objectParts[0]] && 2 === count($objectParts)) {
                             $object = $this->prefixes[$objectParts[0]].$objectParts[1];
                         }
+
                         $predicateElement->setAttribute($this->prefixedName('rdf:resource'),
                             $this->prefixedName($object, true));
                     } else {
                         if ($properties['language']) {
                             $predicateElement->setAttribute($this->prefixedName('xml:lang'), $properties['language']);
                         }
+
                         if ($properties['type']) {
                             $predicateElement->setAttribute($this->prefixedName('rdf:datatype'),
                                 $this->prefixedName($properties['type'], true));
diff --git a/Classes/ViewHelpers/LinkedData/Renderer/TurtleRenderer.php b/Classes/ViewHelpers/LinkedData/Renderer/TurtleRenderer.php
index 44edf143..ce606fdf 100644
--- a/Classes/ViewHelpers/LinkedData/Renderer/TurtleRenderer.php
+++ b/Classes/ViewHelpers/LinkedData/Renderer/TurtleRenderer.php
@@ -59,29 +59,28 @@ public function renderItems($items)
                         $objectString = $this->turtleString($object);
                     } else {
                         if (false === strpos($object, '"') && false === strpos($object, "\r") && false === strpos($object,
-                                "\n")
-                        ) {
+                                "\n")) {
                             $objectString = '"'.$object.'"';
+                        } elseif (false === strpos($object, '"""')) {
+                            $objectString = '"""'.$object.'"""';
+                        } elseif (false === strpos($object, "'''")) {
+                            $objectString = "'''".$object."'''";
                         } else {
-                            if (false === strpos($object, '"""')) {
-                                $objectString = '"""'.$object.'"""';
-                            } else {
-                                if (false === strpos($object, "'''")) {
-                                    $objectString = "'''".$object."'''";
-                                } else {
-                                    // TODO: Error Handling for could not escape.
-                                }
-                            }
+                            // TODO: Error Handling for could not escape.
                         }
+
                         if ($properties['language']) {
                             $objectString .= '@'.$properties['language'];
                         }
+
                         if ($properties['type']) {
                             $objectString .= '^^'.$this->turtleString($properties['type']);
                         }
                     }
+
                     $objectArray[] = $objectString;
                 }
+
                 $predicateString .= implode(', ', $objectArray);
                 $predicateArray[] = $predicateString;
             }
@@ -89,6 +88,7 @@ public function renderItems($items)
             $subjectString .= implode(" ;\n\t", $predicateArray);
             $subjectArray[] = $subjectString;
         }
+
         $result .= implode(' .'.PHP_EOL.PHP_EOL, $subjectArray).' .'.PHP_EOL;
 
         // Prepend the prefixes that are used.
@@ -99,9 +99,7 @@ public function renderItems($items)
             }
         }
 
-        $result = PHP_EOL.implode('', $prefixes).PHP_EOL.$result;
-
-        return $result;
+        return PHP_EOL.implode('', $prefixes).PHP_EOL.$result;
     }
 
     /**
@@ -117,23 +115,18 @@ protected function turtleString($item, $usePrefixes = true)
         $itemParts = explode(':', $item, 2);
         $rdfTypeURI = 'http://www.w3.org/1999/02/22-rdf-syntax-ns#type';
         if ($item === $rdfTypeURI
-            || (count($itemParts) > 1 && $this->prefixes[$itemParts[0]].$itemParts[1] === $rdfTypeURI)
-        ) {
+            || (count($itemParts) > 1 && $this->prefixes[$itemParts[0]].$itemParts[1] === $rdfTypeURI)) {
             $result = 'a';
-        } else {
-            if ($usePrefixes) {
-                foreach ($this->prefixes as $acronym => $prefix) {
-                    if (0 === strpos($item, $prefix)) {
-                        $result = str_replace($prefix, $acronym.':', $item);
-                        $this->usedPrefixes[$acronym] = true;
-                        break;
-                    } else {
-                        if ($itemParts[0] === $acronym) {
-                            $result = $item;
-                            $this->usedPrefixes[$acronym] = true;
-                            break;
-                        }
-                    }
+        } elseif ($usePrefixes) {
+            foreach ($this->prefixes as $acronym => $prefix) {
+                if (0 === strpos($item, $prefix)) {
+                    $result = str_replace($prefix, $acronym.':', $item);
+                    $this->usedPrefixes[$acronym] = true;
+                    break;
+                } elseif ($itemParts[0] === $acronym) {
+                    $result = $item;
+                    $this->usedPrefixes[$acronym] = true;
+                    break;
                 }
             }
         }
diff --git a/Classes/ViewHelpers/Logic/NotViewHelper.php b/Classes/ViewHelpers/Logic/NotViewHelper.php
index 11185f7c..2337d07a 100644
--- a/Classes/ViewHelpers/Logic/NotViewHelper.php
+++ b/Classes/ViewHelpers/Logic/NotViewHelper.php
@@ -46,14 +46,11 @@ public function initializeArguments()
         $this->registerArgument('condition', 'string|int|float|array', 'the condition to NOT', true);
     }
 
-    /**
-     * @return bool
-     */
     public static function renderStatic(
         array $arguments,
         \Closure $renderChildrenClosure,
         RenderingContextInterface $renderingContext
-    ) {
-        return !(true == $arguments['condition']);
+    ): bool {
+        return true != $arguments['condition'];
     }
 }
diff --git a/Configuration/TCA/Overrides/tt_content.php b/Configuration/TCA/Overrides/tt_content.php
index ed89ae3d..94f70a1a 100644
--- a/Configuration/TCA/Overrides/tt_content.php
+++ b/Configuration/TCA/Overrides/tt_content.php
@@ -1,7 +1,7 @@
 <?php
 
 \TYPO3\CMS\Extbase\Utility\ExtensionUtility::registerPlugin(
-    'Subugoe.find',
+    'Find',
     'find',
     'find'
 );
diff --git a/README.md b/README.md
index b451b584..90f6f5ae 100644
--- a/README.md
+++ b/README.md
@@ -40,7 +40,8 @@ For the most basic example you need to:
                 options {
                     host = solr.local
                     port = 8080
-                    path = /solr/myIndex
+                    path = /
+                    core = myIndex
                 }
             }
         }
@@ -965,8 +966,8 @@ depending on the `id` s used for fields and facets.
 
 ## Prerequisites
 
-- TYPO3 8.7
-- PHP 7.1 or higher
+- TYPO3 10.4
+- PHP 7.4 or higher
 
 ## Testing
 
@@ -974,6 +975,13 @@ To run the unit tests, clone this repository, and run
 * `composer install`
 * `.Build/bin/phpunit --colors -c .Build/vendor/nimut/testing-framework/res/Configuration/UnitTests.xml Tests/Unit/`
 
+## Contributing
+
+Open a pull request on Github.
+
+Make sure to run `composer lint` before to see, if the coding style is met.
+If not, this can be automatically fixed with `composer fix`.
+
 Contact
 -------
 
diff --git a/Tests/Unit/Controller/SearchControllerTest.php b/Tests/Unit/Controller/SearchControllerTest.php
index 3c980729..98efc546 100644
--- a/Tests/Unit/Controller/SearchControllerTest.php
+++ b/Tests/Unit/Controller/SearchControllerTest.php
@@ -38,7 +38,7 @@ class SearchControllerTest extends \Nimut\TestingFramework\TestCase\UnitTestCase
      */
     protected $fixture;
 
-    public function setUp()
+    protected function setUp(): void
     {
         $this->fixture = $this->getMockBuilder(SearchController::class)
             ->disableOriginalConstructor()
diff --git a/Tests/Unit/Service/SolrServiceProviderTest.php b/Tests/Unit/Service/SolrServiceProviderTest.php
index 4e760a9b..a38bc48f 100644
--- a/Tests/Unit/Service/SolrServiceProviderTest.php
+++ b/Tests/Unit/Service/SolrServiceProviderTest.php
@@ -40,7 +40,7 @@ class SolrServiceProviderTest extends UnitTestCase
      */
     protected $fixture;
 
-    public function setUp()
+    protected function setUp(): void
     {
         $this->fixture = $this->getMockBuilder(SolrServiceProvider::class)
             ->setMethods(['dummy'])
diff --git a/Tests/Unit/Utility/UpgradeUtilityTest.php b/Tests/Unit/Utility/UpgradeUtilityTest.php
new file mode 100644
index 00000000..88515e92
--- /dev/null
+++ b/Tests/Unit/Utility/UpgradeUtilityTest.php
@@ -0,0 +1,72 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Subugoe\Find\Tests\Unit\Utility;
+
+use PHPUnit\Framework\TestCase;
+use Subugoe\Find\Utility\UpgradeUtility;
+
+class UpgradeUtilityTest extends TestCase
+{
+    public function settingsProvider(): array
+    {
+        return [
+            [
+                [
+                    'host' => 'solr',
+                    'port' => 8983,
+                    'path' => '/solr/core_en',
+                    'scheme' => 'http',
+                ],
+                [
+                    'host' => 'solr',
+                    'port' => 8983,
+                    'path' => '/',
+                    'scheme' => 'http',
+                    'core' => 'core_en',
+                ],
+            ],
+            [
+                [
+                    'host' => 'solr',
+                    'port' => 8983,
+                    'path' => '/solr/core_en/',
+                    'scheme' => 'http',
+                ],
+                [
+                    'host' => 'solr',
+                    'port' => 8983,
+                    'path' => '/',
+                    'scheme' => 'http',
+                    'core' => 'core_en',
+                ],
+            ],
+            [
+                [
+                    'host' => 'solr.local',
+                    'port' => 8983,
+                    'path' => '/',
+                    'scheme' => 'http',
+                    'core' => 'core_en',
+                ],
+                [
+                    'host' => 'solr.local',
+                    'port' => 8983,
+                    'path' => '/',
+                    'scheme' => 'http',
+                    'core' => 'core_en',
+                ],
+            ],
+        ];
+    }
+
+    /**
+     * @test
+     * @dataProvider settingsProvider
+     */
+    public function configurationIsAutomaticallyUpgraded(array $settings, $expected): void
+    {
+        self::assertSame($expected, UpgradeUtility::handleSolariumUpgrade($settings));
+    }
+}
diff --git a/Tests/Unit/ViewHelpers/Data/ArrayFirstViewHelperTest.php b/Tests/Unit/ViewHelpers/Data/ArrayFirstViewHelperTest.php
index 5a0f4957..243ad201 100644
--- a/Tests/Unit/ViewHelpers/Data/ArrayFirstViewHelperTest.php
+++ b/Tests/Unit/ViewHelpers/Data/ArrayFirstViewHelperTest.php
@@ -39,7 +39,7 @@ class ArrayFirstViewHelperTest extends ViewHelperBaseTestcase
      */
     public $fixture;
 
-    public function setUp()
+    protected function setUp(): void
     {
         parent::setUp();
         $this->fixture = $this->getMockBuilder(ArrayFirstViewHelper::class)
diff --git a/Tests/Unit/ViewHelpers/Data/IsArrayViewHelperTest.php b/Tests/Unit/ViewHelpers/Data/IsArrayViewHelperTest.php
index 2cf783f6..aac1d2eb 100644
--- a/Tests/Unit/ViewHelpers/Data/IsArrayViewHelperTest.php
+++ b/Tests/Unit/ViewHelpers/Data/IsArrayViewHelperTest.php
@@ -39,7 +39,7 @@ class IsArrayViewHelperTest extends ViewHelperBaseTestcase
      */
     public $fixture;
 
-    public function setUp()
+    protected function setUp(): void
     {
         parent::setUp();
         $this->fixture = $this->getMockBuilder(IsArrayViewHelper::class)
diff --git a/Tests/Unit/ViewHelpers/Data/NewArrayViewHelperTest.php b/Tests/Unit/ViewHelpers/Data/NewArrayViewHelperTest.php
index 091da8a4..cfbbb40d 100644
--- a/Tests/Unit/ViewHelpers/Data/NewArrayViewHelperTest.php
+++ b/Tests/Unit/ViewHelpers/Data/NewArrayViewHelperTest.php
@@ -39,7 +39,7 @@ class NewArrayViewHelperTest extends ViewHelperBaseTestcase
      */
     public $fixture;
 
-    public function setUp()
+    protected function setUp(): void
     {
         parent::setUp();
         $this->fixture = $this->getMockBuilder(NewArrayViewHelper::class)
diff --git a/Tests/Unit/ViewHelpers/Data/SplitViewHelperTest.php b/Tests/Unit/ViewHelpers/Data/SplitViewHelperTest.php
index 8f9aa509..e0355f57 100644
--- a/Tests/Unit/ViewHelpers/Data/SplitViewHelperTest.php
+++ b/Tests/Unit/ViewHelpers/Data/SplitViewHelperTest.php
@@ -39,7 +39,7 @@ class SplitViewHelperTest extends ViewHelperBaseTestcase
      */
     public $fixture;
 
-    public function setUp()
+    protected function setUp(): void
     {
         parent::setUp();
 
diff --git a/Tests/Unit/ViewHelpers/Data/TransposeViewHelperTest.php b/Tests/Unit/ViewHelpers/Data/TransposeViewHelperTest.php
index e518e8f3..ab428788 100644
--- a/Tests/Unit/ViewHelpers/Data/TransposeViewHelperTest.php
+++ b/Tests/Unit/ViewHelpers/Data/TransposeViewHelperTest.php
@@ -45,7 +45,7 @@ class TransposeViewHelperTest extends ViewHelperBaseTestcase
      */
     public $templateVariableContainer;
 
-    public function setUp()
+    protected function setUp(): void
     {
         parent::setUp();
         $this->fixture = $this->getMockBuilder(TransposeViewHelper::class)
@@ -97,7 +97,7 @@ public function anErrorIsReportedWhenArraysDoNotMatchInLength()
         ];
 
         $this->fixture->setArguments($arguments);
-        self::assertContains('The arrays passed in the »arrays« argument do not have identical numbers of values',
+        self::assertStringContainsStringIgnoringCase('The arrays passed in the »arrays« argument do not have identical numbers of values',
             $this->fixture->initializeArgumentsAndRender());
     }
 }
diff --git a/Tests/Unit/ViewHelpers/Data/ValueForKeyViewHelperTest.php b/Tests/Unit/ViewHelpers/Data/ValueForKeyViewHelperTest.php
index a49a61e0..182e4f6f 100644
--- a/Tests/Unit/ViewHelpers/Data/ValueForKeyViewHelperTest.php
+++ b/Tests/Unit/ViewHelpers/Data/ValueForKeyViewHelperTest.php
@@ -42,7 +42,7 @@ class ValueForKeyViewHelperTest extends ViewHelperBaseTestcase
      */
     public $fixture;
 
-    public function setUp()
+    protected function setUp(): void
     {
         parent::setUp();
 
diff --git a/Tests/Unit/ViewHelpers/Find/FacetIsActiveViewHelperTest.php b/Tests/Unit/ViewHelpers/Find/FacetIsActiveViewHelperTest.php
index 9aa46f56..f92bba0b 100644
--- a/Tests/Unit/ViewHelpers/Find/FacetIsActiveViewHelperTest.php
+++ b/Tests/Unit/ViewHelpers/Find/FacetIsActiveViewHelperTest.php
@@ -39,7 +39,7 @@ class FacetIsActiveViewHelperTest extends ViewHelperBaseTestcase
      */
     public $fixture;
 
-    public function setUp()
+    protected function setUp(): void
     {
         parent::setUp();
         $this->fixture = $this->getAccessibleMock(FacetIsActiveViewHelper::class, ['renderChildren']);
diff --git a/Tests/Unit/ViewHelpers/Find/FacetLinkArgumentsViewHelperTest.php b/Tests/Unit/ViewHelpers/Find/FacetLinkArgumentsViewHelperTest.php
index e7b86693..274cba03 100644
--- a/Tests/Unit/ViewHelpers/Find/FacetLinkArgumentsViewHelperTest.php
+++ b/Tests/Unit/ViewHelpers/Find/FacetLinkArgumentsViewHelperTest.php
@@ -42,7 +42,7 @@ class FacetLinkArgumentsViewHelperTest extends ViewHelperBaseTestcase
      */
     public $fixture;
 
-    public function setUp()
+    protected function setUp(): void
     {
         parent::setUp();
         $this->fixture = $this->getMockBuilder(FacetLinkArgumentsViewHelper::class)
diff --git a/Tests/Unit/ViewHelpers/Find/HighlightFieldViewHelperTest.php b/Tests/Unit/ViewHelpers/Find/HighlightFieldViewHelperTest.php
index 58a137d7..67f3e34c 100644
--- a/Tests/Unit/ViewHelpers/Find/HighlightFieldViewHelperTest.php
+++ b/Tests/Unit/ViewHelpers/Find/HighlightFieldViewHelperTest.php
@@ -43,7 +43,7 @@ class HighlightFieldViewHelperTest extends ViewHelperBaseTestcase
 
     protected $solariumResponse;
 
-    public function setUp()
+    protected function setUp(): void
     {
         parent::setUp();
 
diff --git a/Tests/Unit/ViewHelpers/Find/PageNumberForResultNumberViewHelperTest.php b/Tests/Unit/ViewHelpers/Find/PageNumberForResultNumberViewHelperTest.php
index b259ac6e..f14b7480 100644
--- a/Tests/Unit/ViewHelpers/Find/PageNumberForResultNumberViewHelperTest.php
+++ b/Tests/Unit/ViewHelpers/Find/PageNumberForResultNumberViewHelperTest.php
@@ -42,7 +42,7 @@ class PageNumberForResultNumberViewHelperTest extends ViewHelperBaseTestcase
      */
     public $fixture;
 
-    public function setUp()
+    protected function setUp(): void
     {
         parent::setUp();
 
diff --git a/Tests/Unit/ViewHelpers/Find/PathExistsViewHelperTest.php b/Tests/Unit/ViewHelpers/Find/PathExistsViewHelperTest.php
index 61f70914..f6885b83 100644
--- a/Tests/Unit/ViewHelpers/Find/PathExistsViewHelperTest.php
+++ b/Tests/Unit/ViewHelpers/Find/PathExistsViewHelperTest.php
@@ -39,7 +39,7 @@ class PathExistsViewHelperTest extends ViewHelperBaseTestcase
      */
     public $fixture;
 
-    public function setUp()
+    protected function setUp(): void
     {
         parent::setUp();
         $this->fixture = $this->getAccessibleMock(PathExistsViewHelper::class, ['renderChildren']);
diff --git a/Tests/Unit/ViewHelpers/Find/SelectOptionsForFacetViewHelperTest.php b/Tests/Unit/ViewHelpers/Find/SelectOptionsForFacetViewHelperTest.php
index 862d99d6..e45e0db3 100644
--- a/Tests/Unit/ViewHelpers/Find/SelectOptionsForFacetViewHelperTest.php
+++ b/Tests/Unit/ViewHelpers/Find/SelectOptionsForFacetViewHelperTest.php
@@ -39,7 +39,7 @@ class SelectOptionsForFacetViewHelperTest extends ViewHelperBaseTestcase
      */
     public $fixture;
 
-    public function setUp()
+    protected function setUp(): void
     {
         parent::setUp();
         $this->fixture = $this->getMockBuilder(SelectOptionsForFacetViewHelper::class)
diff --git a/Tests/Unit/ViewHelpers/Format/CSVLineViewHelperTest.php b/Tests/Unit/ViewHelpers/Format/CSVLineViewHelperTest.php
index c96f4259..42599266 100644
--- a/Tests/Unit/ViewHelpers/Format/CSVLineViewHelperTest.php
+++ b/Tests/Unit/ViewHelpers/Format/CSVLineViewHelperTest.php
@@ -40,7 +40,7 @@ class CSVLineViewHelperTest extends ViewHelperBaseTestcase
      */
     protected $fixture;
 
-    public function setUp()
+    protected function setUp(): void
     {
         parent::setUp();
 
diff --git a/Tests/Unit/ViewHelpers/Format/JoinViewHelperTest.php b/Tests/Unit/ViewHelpers/Format/JoinViewHelperTest.php
index 30df1365..6fefb146 100644
--- a/Tests/Unit/ViewHelpers/Format/JoinViewHelperTest.php
+++ b/Tests/Unit/ViewHelpers/Format/JoinViewHelperTest.php
@@ -40,7 +40,7 @@ class JoinViewHelperTest extends ViewHelperBaseTestcase
      */
     protected $fixture;
 
-    public function setUp()
+    protected function setUp(): void
     {
         parent::setUp();
 
diff --git a/Tests/Unit/ViewHelpers/Format/RegexpViewHelperTest.php b/Tests/Unit/ViewHelpers/Format/RegexpViewHelperTest.php
index 396893f6..f79906ed 100644
--- a/Tests/Unit/ViewHelpers/Format/RegexpViewHelperTest.php
+++ b/Tests/Unit/ViewHelpers/Format/RegexpViewHelperTest.php
@@ -68,7 +68,7 @@ public function regexProvider()
         ];
     }
 
-    public function setUp()
+    protected function setUp(): void
     {
         parent::setUp();
         $this->fixture = $this->getMockBuilder(RegexpViewHelper::class)
diff --git a/Tests/Unit/ViewHelpers/Format/StripViewHelperTest.php b/Tests/Unit/ViewHelpers/Format/StripViewHelperTest.php
index eab288e9..1da5152d 100644
--- a/Tests/Unit/ViewHelpers/Format/StripViewHelperTest.php
+++ b/Tests/Unit/ViewHelpers/Format/StripViewHelperTest.php
@@ -53,7 +53,7 @@ public function stringProvider()
         ];
     }
 
-    public function setUp()
+    protected function setUp(): void
     {
         parent::setUp();
         $this->fixture = $this->getMockBuilder(StripViewHelper::class)
diff --git a/Tests/Unit/ViewHelpers/Format/XMLViewHelperTest.php b/Tests/Unit/ViewHelpers/Format/XMLViewHelperTest.php
index b1a3b08d..fee95797 100644
--- a/Tests/Unit/ViewHelpers/Format/XMLViewHelperTest.php
+++ b/Tests/Unit/ViewHelpers/Format/XMLViewHelperTest.php
@@ -61,7 +61,7 @@ public function stringProvider()
         ];
     }
 
-    public function setUp()
+    protected function setUp(): void
     {
         parent::setUp();
         $this->fixture = $this->getMockBuilder(XMLViewHelper::class)
diff --git a/Tests/Unit/ViewHelpers/LinkedData/ItemViewHelperTest.php b/Tests/Unit/ViewHelpers/LinkedData/ItemViewHelperTest.php
index a4e072a0..7ae456c2 100644
--- a/Tests/Unit/ViewHelpers/LinkedData/ItemViewHelperTest.php
+++ b/Tests/Unit/ViewHelpers/LinkedData/ItemViewHelperTest.php
@@ -59,7 +59,7 @@ public function linkedDataProvider()
         ];
     }
 
-    public function setUp()
+    protected function setUp(): void
     {
         parent::setUp();
         $this->fixture = $this->getMockBuilder(ItemViewHelper::class)
diff --git a/Tests/Unit/ViewHelpers/Logic/AndViewHelperTest.php b/Tests/Unit/ViewHelpers/Logic/AndViewHelperTest.php
index 20943ddd..563bfe71 100644
--- a/Tests/Unit/ViewHelpers/Logic/AndViewHelperTest.php
+++ b/Tests/Unit/ViewHelpers/Logic/AndViewHelperTest.php
@@ -61,7 +61,7 @@ public function conditionProvider()
                     (true === true),
                     (1 === 1),
                     ('hrdr' === 'hrdr'),
-                    ('hrdr' == 'hrdr'),
+                    ('hrdr' === 'hrdr'),
                     (true == 1),
                 ],
                 true,
@@ -71,7 +71,7 @@ public function conditionProvider()
                     (true === true),
                     (1 === 2),
                     ('hrdr' === 'hrdr'),
-                    ('hrdr' == 'hrdr'),
+                    ('hrdr' === 'hrdr'),
                     (true == 1),
                 ],
                 false,
@@ -87,7 +87,7 @@ public function conditionProvider()
                     (true === true),
                     (1 === 1),
                     ('hrdr' === 'hrdr'),
-                    ('hrdr' == 'hrdr'),
+                    ('hrdr' === 'hrdr'),
                     (true == 0),
                 ],
                 false,
@@ -95,7 +95,7 @@ public function conditionProvider()
         ];
     }
 
-    public function setUp()
+    protected function setUp(): void
     {
         parent::setUp();
         $this->fixture = $this->getMockBuilder(AndViewHelper::class)
diff --git a/Tests/Unit/ViewHelpers/Logic/NotViewHelperTest.php b/Tests/Unit/ViewHelpers/Logic/NotViewHelperTest.php
index b4a5395f..dd98d15f 100644
--- a/Tests/Unit/ViewHelpers/Logic/NotViewHelperTest.php
+++ b/Tests/Unit/ViewHelpers/Logic/NotViewHelperTest.php
@@ -40,10 +40,7 @@ class NotViewHelperTest extends ViewHelperBaseTestcase
      */
     protected $fixture;
 
-    /**
-     * @return array
-     */
-    public function conditionProvider()
+    public function conditionProvider(): array
     {
         return [
             [
@@ -51,7 +48,7 @@ public function conditionProvider()
                 true,
             ],
             [
-                1,
+                (bool) 1,
                 true,
             ],
             [
@@ -65,7 +62,7 @@ public function conditionProvider()
         ];
     }
 
-    public function setUp()
+    protected function setUp(): void
     {
         parent::setUp();
         $this->fixture = $this->getMockBuilder(NotViewHelper::class)
@@ -78,7 +75,7 @@ public function setUp()
      * @test
      * @dataProvider conditionProvider
      */
-    public function conditionIsMet(bool $conditions, bool $expected)
+    public function conditionIsMet(bool $conditions, bool $expected): void
     {
         $this->fixture->setArguments([
             'conditions' => $conditions,
diff --git a/Tests/Unit/ViewHelpers/Logic/OrViewHelperTest.php b/Tests/Unit/ViewHelpers/Logic/OrViewHelperTest.php
index d3860515..01956bca 100644
--- a/Tests/Unit/ViewHelpers/Logic/OrViewHelperTest.php
+++ b/Tests/Unit/ViewHelpers/Logic/OrViewHelperTest.php
@@ -51,7 +51,7 @@ public function conditionProvider()
                     (true === true),
                     (1 === 1),
                     ('hrdr' === 'hrdr'),
-                    ('hrdr' == 'hrdr'),
+                    ('hrdr' === 'hrdr'),
                     (true == 1),
                 ],
                 true,
@@ -61,7 +61,7 @@ public function conditionProvider()
                     (true === true),
                     (1 === 1),
                     ('hrdr' === 'hrdr'),
-                    ('hrdr' == 'hrdr'),
+                    ('hrdr' === 'hrdr'),
                     (true == 'hrdr'),
                 ],
                 true,
@@ -91,7 +91,7 @@ public function conditionProvider()
         ];
     }
 
-    public function setUp()
+    protected function setUp(): void
     {
         parent::setUp();
         $this->fixture = $this->getMockBuilder(OrViewHelper::class)
diff --git a/UPGRADING.md b/UPGRADING.md
new file mode 100644
index 00000000..1261a97f
--- /dev/null
+++ b/UPGRADING.md
@@ -0,0 +1,44 @@
+# Upgrading the find extension
+
+## Solarium upgrade
+
+The underlying solarium library has been updated. Find tries so do this as smooth as possible
+for you.
+
+Solr has a slightly changed syntax for connecting now, see [here](https://solarium.readthedocs.io/en/stable/getting-started/#pitfall-when-upgrading-from-earlier-versions-to-5x).
+
+This is the actual syntax:
+
+```
+plugin.tx_find.settings {
+    connections {
+        default {
+            options {
+                host = solr.local
+                port = 8983
+                path = /
+                scheme = http
+                core = myIndex
+            }
+        }
+    }
+}
+```
+
+
+The connection configuration below may still work, but a deprecation notice is thrown - so
+please change the settings.
+
+```
+plugin.tx_find.settings {
+    connections {
+        default {
+            options {
+                host = solr.local
+                port = 8080
+                path = /solr/myIndex
+            }
+        }
+    }
+}
+```
diff --git a/composer.json b/composer.json
index cbb9d04d..bf3aad53 100644
--- a/composer.json
+++ b/composer.json
@@ -26,27 +26,46 @@
     }
   },
   "replace": {
-    "typo3-ter/find": "self.version",
-    "subugoe/find": "self.version"
+    "typo3-ter/find": "self.version"
   },
   "require": {
+    "php": "^7.4",
+    "ext-curl": "*",
     "ext-json": "*",
-    "typo3/cms-core": "^9.5 || ^10.4.10",
-    "typo3/cms-felogin": "^9.5 || ^10.4.10"
+    "solarium/solarium": ">=6.0 <7.0",
+    "typo3/cms-core": "^10.4.10",
+    "typo3/cms-felogin": "^10.4.10"
   },
   "require-dev": {
-    "solarium/solarium": "~4.2 || ^5.1",
-    "nimut/testing-framework": "^5.1",
-    "friendsofphp/php-cs-fixer": "^2.13"
+    "nimut/testing-framework": "^6.0",
+    "friendsofphp/php-cs-fixer": "^3.0",
+    "phpunit/phpunit": "^8.5",
+    "rector/rector": "^0.12.5"
   },
   "config": {
     "vendor-dir": ".Build/vendor",
-    "bin-dir": ".Build/bin"
+    "bin-dir": ".Build/bin",
+    "allow-plugins": {
+      "typo3/class-alias-loader": true,
+      "typo3/cms-composer-installers": true
+    }
   },
   "scripts": {
     "post-autoload-dump": [
       "mkdir -p .Build/Web/typo3conf/ext/",
       "[ -L .Build/Web/typo3conf/ext/find ] || ln -snvf ../../../../. .Build/Web/typo3conf/ext/find"
+    ],
+    "rector-lint": ".Build/bin/rector process --dry-run",
+    "rector-fix": ".Build/bin/rector process",
+    "php-cs-lint": ".Build/bin/php-cs-fixer fix --dry-run",
+    "php-cs-fix": ".Build/bin/php-cs-fixer fix",
+    "lint":  [
+      "@php-cs-lint",
+      "@rector-lint"
+    ],
+    "fix":  [
+      "@php-cs-fix",
+      "@rector-fix"
     ]
   },
   "suggest": {
diff --git a/ext_emconf.php b/ext_emconf.php
index bb28ea85..1678f26c 100755
--- a/ext_emconf.php
+++ b/ext_emconf.php
@@ -1,30 +1,20 @@
 <?php
 
-$EM_CONF[$_EXTKEY] = [
+$EM_CONF['find'] = [
     'title' => 'Find',
     'description' => 'A frontend for Solr indexes',
     'version' => '3.1.1',
     'state' => 'stable',
     'category' => 'frontend',
-    'shy' => 0,
-    'priority' => '',
-    'loadOrder' => '',
-    'module' => '',
-    'uploadfolder' => 0,
-    'createDirs' => '',
-    'modify_tables' => '',
-    'clearcacheonload' => 1,
-    'lockType' => '',
+    'clearCacheOnLoad' => true,
     'author' => 'Sven-S. Porst, Ingo Pfennigstorf',
     'author_email' => 'pfennigstorf@sub.uni-goettingen.de',
     'author_company' => 'SUB Göttingen',
-    'dependencies' => '',
-    'conflicts' => '',
     'constraints' => [
         'depends' => [
-            'php' => '7.2.0-7.4.99',
-            'typo3' => '9.5.0-10.4.99',
-            'felogin' => '9.5.0-10.4.99',
+            'php' => '7.4.0-8.0.99',
+            'typo3' => '10.4.0-10.4.99',
+            'felogin' => '10.4.0-10.4.99',
         ],
         'conflicts' => [],
         'suggests' => [],
diff --git a/ext_localconf.php b/ext_localconf.php
index 30adbaa0..f6a7f216 100644
--- a/ext_localconf.php
+++ b/ext_localconf.php
@@ -1,17 +1,17 @@
 <?php
 
-if (!defined('TYPO3_COMPOSER_MODE') || TYPO3_COMPOSER_MODE === false) {
+if (!defined('TYPO3_COMPOSER_MODE') || !TYPO3_COMPOSER_MODE) {
     require_once \TYPO3\CMS\Core\Utility\ExtensionManagementUtility::extPath('find').'.Build/vendor/autoload.php';
 }
 
 \TYPO3\CMS\Extbase\Utility\ExtensionUtility::configurePlugin(
-    'Subugoe.find',
+    'Find',
     'Find',
     [
-        'Search' => 'index, detail, suggest',
+        \Subugoe\Find\Controller\SearchController::class => 'index, detail, suggest',
     ],
     [
-        'Search' => 'index, detail, suggest',
+        \Subugoe\Find\Controller\SearchController::class => 'index, detail, suggest',
     ]
 );
 
diff --git a/rector.php b/rector.php
new file mode 100644
index 00000000..8ce7ad68
--- /dev/null
+++ b/rector.php
@@ -0,0 +1,31 @@
+<?php
+
+declare(strict_types=1);
+
+use Rector\Config\RectorConfig;
+use Rector\Set\ValueObject\SetList;
+use Ssch\TYPO3Rector\Set\Typo3SetList;
+
+return static function (RectorConfig $containerConfigurator): void {
+    $containerConfigurator->paths([
+        __DIR__.'/Classes',
+        __DIR__.'/Tests',
+        __DIR__.'/Configuration',
+        __DIR__.'/Resources',
+        __DIR__.'/*.php',
+    ]);
+    $containerConfigurator->skip([
+        __DIR__.'/.Build/vendor',
+        __DIR__.'/var',
+        __DIR__.'/*.cache',
+    ]);
+
+    // Define what rule sets will be applied
+    $containerConfigurator->sets([
+        SetList::CODING_STYLE,
+        SetList::CODE_QUALITY,
+        SetList::PHP_74,
+        Typo3SetList::TYPO3_104,
+        Typo3SetList::TYPOSCRIPT_CONDITIONS_104,
+    ]);
+};