diff --git a/.github/workflows/coding-standards.yml b/.github/workflows/coding-standards.yml
index ee78d555..b3370342 100644
--- a/.github/workflows/coding-standards.yml
+++ b/.github/workflows/coding-standards.yml
@@ -10,7 +10,7 @@ on:
 jobs:
 
   php-cs-fixer:
-    name: linter
+    name: PHP CS Fixer
     runs-on: ubuntu-latest
 
     steps:
@@ -19,10 +19,44 @@ jobs:
         uses: actions/checkout@v3
 
       - name: Setup PHP with Composer and extensions
+        uses: shivammathur/setup-php@v2
         with:
           php-version: 8.1
           tools: php-cs-fixer
-        uses: shivammathur/setup-php@v2
 
       - name: Run php-cs-fixer
         run: php-cs-fixer fix --diff --dry-run --allow-risky=yes --using-cache=no
+
+  phpstan:
+     name: PHPStan
+     runs-on: ubuntu-latest
+
+     steps:
+
+       - name: Checkout
+         uses: actions/checkout@v3
+
+       - name: Setup PHP with Composer and extensions
+         uses: shivammathur/setup-php@v2
+         with:
+           php-version: 8.2
+           tools: phpstan
+
+       - name: Get Composer cache directory
+         id: composer-cache
+         run: echo "directory=$(composer config cache-dir)" >> $GITHUB_OUTPUT
+
+       - name: Cache Composer dependencies
+         uses: actions/cache@v3
+         with:
+           path: ${{ steps.composer-cache.outputs.directory }}
+           key: tests-php-${{ matrix.php }}-composer-${{ hashFiles('**/composer.lock') }}
+           restore-keys: tests-php-${{ matrix.php }}-composer
+
+       - name: Install Composer dependencies
+         env:
+           PHP_VERSION: ${{ matrix.php }}
+         run: composer install --ansi --no-progress --prefer-dist $(if [ "$PHP_VERSION" == "8.0" ]; then echo "--ignore-platform-reqs"; fi;)
+
+       - name: Run PHPStan
+         run: phpstan analyse
diff --git a/phpstan.dist.neon b/phpstan.dist.neon
new file mode 100644
index 00000000..c0603cff
--- /dev/null
+++ b/phpstan.dist.neon
@@ -0,0 +1,25 @@
+parameters:
+  level: 0
+
+  paths:
+    - src
+    - tests
+
+  ignoreErrors:
+    - '#^Function phpiredis_\w+ not found\.$#'
+    -
+      message: "#^Unsafe usage of new static\\(\\)\\.$#"
+      count: 3
+      path: src/Client.php
+    -
+      message: "#^Unsafe usage of new static\\(\\)\\.$#"
+      count: 1
+      path: src/Connection/Parameters.php
+    -
+      message: "#^Static method Predis\\\\Command\\\\RawCommand\\:\\:create\\(\\) invoked with 0 parameters, at least 1 required\\.$#"
+      count: 1
+      path: tests/Predis/Command/RawCommandTest.php
+    -
+      message: "#^Call to an undefined method Predis\\\\Configuration\\\\Option\\\\AggregateTest\\:\\:getMockConnectionClass\\(\\)\\.$#"
+      count: 2
+      path: tests/Predis/Configuration/Option/AggregateTest.php
diff --git a/src/Cluster/SlotMap.php b/src/Cluster/SlotMap.php
index 5ed0d3e6..5ca1896b 100644
--- a/src/Cluster/SlotMap.php
+++ b/src/Cluster/SlotMap.php
@@ -17,6 +17,7 @@ use ArrayIterator;
 use Countable;
 use IteratorAggregate;
 use OutOfBoundsException;
+use Predis\Connection\NodeConnectionInterface;
 use ReturnTypeWillChange;
 
 /**
@@ -144,7 +145,7 @@ class SlotMap implements ArrayAccess, IteratorAggregate, Countable
      *
      * @param int $slot Slot index.
      *
-     * @return string
+     * @return ?string
      */
     #[ReturnTypeWillChange]
     public function offsetGet($slot)
@@ -152,6 +153,8 @@ class SlotMap implements ArrayAccess, IteratorAggregate, Countable
         if (isset($this->slots[$slot])) {
             return $this->slots[$slot];
         }
+
+        return null;
     }
 
     /**
@@ -159,8 +162,6 @@ class SlotMap implements ArrayAccess, IteratorAggregate, Countable
      *
      * @param int                            $slot       Slot index.
      * @param NodeConnectionInterface|string $connection ID or connection instance.
-     *
-     * @return string
      */
     #[ReturnTypeWillChange]
     public function offsetSet($slot, $connection)
@@ -176,8 +177,6 @@ class SlotMap implements ArrayAccess, IteratorAggregate, Countable
      * Returns the node assigned to the specified slot.
      *
      * @param int $slot Slot index.
-     *
-     * @return string
      */
     #[ReturnTypeWillChange]
     public function offsetUnset($slot)
diff --git a/src/Cluster/StrategyInterface.php b/src/Cluster/StrategyInterface.php
index 9cfbc269..83801ae6 100644
--- a/src/Cluster/StrategyInterface.php
+++ b/src/Cluster/StrategyInterface.php
@@ -29,7 +29,7 @@ interface StrategyInterface
      *
      * @param CommandInterface $command Command instance.
      *
-     * @return int
+     * @return int|null
      */
     public function getSlot(CommandInterface $command);
 
@@ -39,7 +39,7 @@ interface StrategyInterface
      *
      * @param string $key Key string.
      *
-     * @return int
+     * @return int|null
      */
     public function getSlotByKey($key);
 
diff --git a/src/Command/Factory.php b/src/Command/Factory.php
index 75433392..c0b7745d 100644
--- a/src/Command/Factory.php
+++ b/src/Command/Factory.php
@@ -56,6 +56,8 @@ abstract class Factory implements FactoryInterface
         if (isset($this->commands[$commandID = strtoupper($commandID)])) {
             return $this->commands[$commandID];
         }
+
+        return null;
     }
 
     /**
diff --git a/src/Configuration/Option/Replication.php b/src/Configuration/Option/Replication.php
index f9353201..00aa9741 100644
--- a/src/Configuration/Option/Replication.php
+++ b/src/Configuration/Option/Replication.php
@@ -68,12 +68,12 @@ class Replication extends Aggregate
         switch ($description) {
             case 'sentinel':
             case 'redis-sentinel':
-                return function ($parameters, $options, $option) {
+                return function ($parameters, $options) {
                     return new SentinelReplication($options->service, $parameters, $options->connections);
                 };
 
             case 'predis':
-                return $this->getDefaultConnectionInitializer($options);
+                return $this->getDefaultConnectionInitializer();
 
             default:
                 throw new InvalidArgumentException(sprintf(
@@ -91,7 +91,7 @@ class Replication extends Aggregate
      */
     protected function getDefaultConnectionInitializer()
     {
-        return function ($parameters, $options, $option) {
+        return function ($parameters, $options) {
             $connection = new MasterSlaveReplication();
 
             if ($options->autodiscovery) {
diff --git a/src/Connection/PhpiredisSocketConnection.php b/src/Connection/PhpiredisSocketConnection.php
index 26a9b4af..c84b5bee 100644
--- a/src/Connection/PhpiredisSocketConnection.php
+++ b/src/Connection/PhpiredisSocketConnection.php
@@ -283,7 +283,7 @@ class PhpiredisSocketConnection extends AbstractConnection
      * @param string              $address    IP address (DNS-resolved from hostname)
      * @param ParametersInterface $parameters Parameters used to initialize the connection.
      *
-     * @return string
+     * @return void
      */
     private function connectWithTimeout($socket, $address, ParametersInterface $parameters)
     {
diff --git a/src/Connection/Replication/MasterSlaveReplication.php b/src/Connection/Replication/MasterSlaveReplication.php
index 613a0581..39142c10 100644
--- a/src/Connection/Replication/MasterSlaveReplication.php
+++ b/src/Connection/Replication/MasterSlaveReplication.php
@@ -221,6 +221,8 @@ class MasterSlaveReplication implements ReplicationInterface
         } elseif ($role === 'slave') {
             return $this->pickSlave();
         }
+
+        return null;
     }
 
     /**
@@ -316,13 +318,15 @@ class MasterSlaveReplication implements ReplicationInterface
     /**
      * Returns a random slave.
      *
-     * @return NodeConnectionInterface
+     * @return ?NodeConnectionInterface
      */
     protected function pickSlave()
     {
         if ($this->slaves) {
             return $this->slaves[array_rand($this->slaves)];
         }
+
+        return null;
     }
 
     /**
diff --git a/tests/Predis/Collection/Iterator/HashKeyTest.php b/tests/Predis/Collection/Iterator/HashKeyTest.php
index bc0b8b99..4a8c0d5e 100644
--- a/tests/Predis/Collection/Iterator/HashKeyTest.php
+++ b/tests/Predis/Collection/Iterator/HashKeyTest.php
@@ -483,7 +483,7 @@ class HashKeyTest extends PredisTestCase
             ->method('getCommandFactory')
             ->willReturn($this->getCommandFactory());
         $client
-            ->expects($this->once(1))
+            ->expects($this->once())
             ->method('hscan')
             ->withConsecutive(
                 ['key:hash', 0, ['MATCH' => 'field:*', 'COUNT' => 2]]
diff --git a/tests/Predis/Command/Redis/EVALSHA_Test.php b/tests/Predis/Command/Redis/EVALSHA_Test.php
index 76d6c984..2978cab0 100644
--- a/tests/Predis/Command/Redis/EVALSHA_Test.php
+++ b/tests/Predis/Command/Redis/EVALSHA_Test.php
@@ -61,7 +61,7 @@ class EVALSHA_Test extends PredisCommandTestCase
      */
     public function testGetScriptHash(): void
     {
-        $command = $this->getCommandWithArgumentsArray([$sha1 = sha1('return true')], 0);
+        $command = $this->getCommandWithArgumentsArray([$sha1 = sha1('return true')]);
         $this->assertSame($sha1, $command->getScriptHash());
     }
 
diff --git a/tests/Predis/Connection/FactoryTest.php b/tests/Predis/Connection/FactoryTest.php
index 8e1f2950..32620456 100644
--- a/tests/Predis/Connection/FactoryTest.php
+++ b/tests/Predis/Connection/FactoryTest.php
@@ -331,7 +331,7 @@ class FactoryTest extends PredisTestCase
         $connection->expects($this->once())
             ->method('getParameters')
             ->will($this->returnValue($parameters));
-        $connection->expects($this->once(1))
+        $connection->expects($this->once())
             ->method('addConnectCommand')
             ->with($this->isRedisCommand('AUTH', ['foobar']));
 
@@ -358,7 +358,7 @@ class FactoryTest extends PredisTestCase
         $connection->expects($this->once())
             ->method('getParameters')
             ->will($this->returnValue($parameters));
-        $connection->expects($this->once(1))
+        $connection->expects($this->once())
             ->method('addConnectCommand')
             ->with($this->isRedisCommand('AUTH', ['myusername', 'foobar']));
 
diff --git a/tests/Predis/Protocol/Text/ProtocolProcessorTest.php b/tests/Predis/Protocol/Text/ProtocolProcessorTest.php
index 5509a8fc..4f4f8d45 100644
--- a/tests/Predis/Protocol/Text/ProtocolProcessorTest.php
+++ b/tests/Predis/Protocol/Text/ProtocolProcessorTest.php
@@ -82,7 +82,7 @@ class ProtocolProcessorTest extends PredisTestCase
 
         $connection = $this->getMockConnectionOfType('Predis\Connection\CompositeConnectionInterface');
         $connection
-            ->expects($this->once(4))
+            ->expects($this->once())
             ->method('readLine')
             ->willReturn('*1');