diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 2ddcbf0..0d84ab9 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -20,40 +20,15 @@ jobs:
           - 6379:6379
 
     strategy:
+      fail-fast: false
       matrix:
         include:
-          # 7.x configurations
-          - php-version: 7.3
-            use-lowest-dependencies: true
-            shared-test-version: 4.x-dev
-          - php-version: 7.3
-            use-lowest-dependencies: false
-            shared-test-version: 4.x-dev
-
-          - php-version: 7.4
-            use-lowest-dependencies: true
-            shared-test-version: 4.x-dev
-          - php-version: 7.4
-            use-lowest-dependencies: false
-            shared-test-version: 4.x-dev
-
-          # 8.0 configurations
-          - php-version: 8.0
-            use-lowest-dependencies: true
-            shared-test-version: 4.x-dev
-          - php-version: 8.0
-            use-lowest-dependencies: false
-            shared-test-version: 5.x-dev
-
           # 8.1 configurations
           - php-version: 8.1
             use-lowest-dependencies: true
-            shared-test-version: 4.x-dev
-          - php-version: 8.1
-            use-lowest-dependencies: false
             shared-test-version: 5.x-dev
           - php-version: 8.1
-            use-lowest-dependencies: false
+            use-lowest-dependencies: true
             shared-test-version: dev-main
 
           # 8.2 configurations
@@ -64,6 +39,14 @@ jobs:
             use-lowest-dependencies: false
             shared-test-version: dev-main
 
+          # 8.3 configurations
+          - php-version: 8.3
+            use-lowest-dependencies: false
+            shared-test-version: 5.x-dev
+          - php-version: 8.3
+            use-lowest-dependencies: false
+            shared-test-version: dev-main
+
     steps:
       - uses: actions/checkout@v4
         with:
diff --git a/.gitignore b/.gitignore
index 35455d5..9998c07 100644
--- a/.gitignore
+++ b/.gitignore
@@ -7,3 +7,4 @@ docs/build
 docs/.phpdoc
 phpunit/
 .phpunit.result.cache
+.php-cs-fixer.cache
diff --git a/.php-cs-fixer.php b/.php-cs-fixer.php
new file mode 100644
index 0000000..174748f
--- /dev/null
+++ b/.php-cs-fixer.php
@@ -0,0 +1,15 @@
+<?php
+
+$finder = PhpCsFixer\Finder::create()->in(__DIR__);
+
+$config = new PhpCsFixer\Config();
+return $config
+    ->setFinder($finder)
+    ->setUsingCache(true)
+    ->setRules([
+        '@PSR2' => true,
+        'blank_line_after_opening_tag' => true,
+        'ordered_imports' => true,
+        'no_unused_imports' => true,
+        'array_syntax' => ['syntax' => 'short'],
+    ]);
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..7a91435
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,19 @@
+.PHONY: help
+help: #! Show this help message
+	@echo 'Usage: make [target] ... '
+	@echo ''
+	@echo 'Targets:'
+	@grep -h -F '#!' $(MAKEFILE_LIST) | grep -v grep | sed 's/:.*#!/:/' | column -t -s":"
+
+.PHONY: test
+test: #! Run unit tests
+	php -d xdebug.mode=coverage vendor/bin/phpunit
+
+.PHONY: coverage
+coverage: #! Run unit tests with test coverage
+	php -d xdebug.mode=coverage vendor/bin/phpunit
+
+.PHONY: lint
+lint: #! Run quality control tools (e.g. psalm)
+	./vendor/bin/psalm --no-cache
+	composer cs-check
diff --git a/composer.json b/composer.json
index 77f4749..faacad4 100644
--- a/composer.json
+++ b/composer.json
@@ -20,11 +20,15 @@
         }
     ],
     "require": {
-        "php": ">=7.3",
-        "launchdarkly/server-sdk": ">=4.0.0 <7.0.0"
+        "php": ">=8.1",
+        "ext-redis": "*",
+        "launchdarkly/server-sdk": ">=6.3.0 <7.0.0"
     },
     "require-dev": {
-        "phpunit/phpunit": "^9"
+        "friendsofphp/php-cs-fixer": "^3.68",
+        "phpunit/php-code-coverage": "^9",
+        "phpunit/phpunit": "^9",
+        "vimeo/psalm": "^5"
     },
     "autoload": {
         "psr-4": {
@@ -38,5 +42,9 @@
     },
     "config": {
         "sort-packages": true
+    },
+    "scripts": {
+        "cs-check": "vendor/bin/php-cs-fixer fix --diff --dry-run --verbose --config=.php-cs-fixer.php",
+        "cs-fix": "vendor/bin/php-cs-fixer fix --diff --verbose --config=.php-cs-fixer.php"
     }
 }
diff --git a/psalm.xml b/psalm.xml
new file mode 100644
index 0000000..4e9226b
--- /dev/null
+++ b/psalm.xml
@@ -0,0 +1,15 @@
+<?xml version="1.0"?>
+<psalm
+    errorLevel="2"
+    resolveFromConfigFile="true"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xmlns="https://getpsalm.org/schema/config"
+    xsi:schemaLocation="https://getpsalm.org/schema/config vendor/vimeo/psalm/config.xsd"
+>
+    <projectFiles>
+        <directory name="src" />
+        <ignoreFiles>
+            <directory name="vendor" />
+        </ignoreFiles>
+    </projectFiles>
+</psalm>
diff --git a/src/LaunchDarkly/Impl/Integrations/PHPRedisFeatureRequester.php b/src/LaunchDarkly/Impl/Integrations/PHPRedisFeatureRequester.php
index 4be9bd0..fcdd0e6 100644
--- a/src/LaunchDarkly/Impl/Integrations/PHPRedisFeatureRequester.php
+++ b/src/LaunchDarkly/Impl/Integrations/PHPRedisFeatureRequester.php
@@ -1,34 +1,34 @@
 <?php
+
 namespace LaunchDarkly\Impl\Integrations;
 
-use LaunchDarkly\Impl\Integrations\FeatureRequesterBase;
+use Redis;
 
 /**
  * @internal
  */
 class PHPRedisFeatureRequester extends FeatureRequesterBase
 {
-    /** @var array */
-    private $_redisOptions;
-    /** @var \Redis */
-    private $_redisInstance;
-    /** @var string */
-    private $_prefix;
+    private ?array $redisOptions = null;
+    private ?Redis $redisInstance = null;
+    private ?string $prefix;
 
-    public function __construct($baseUri, $sdkKey, $options)
+    public function __construct(string $baseUri, string $sdkKey, array $options)
     {
         parent::__construct($baseUri, $sdkKey, $options);
 
-        $this->_prefix = $options['redis_prefix'] ?? null;
-        if ($this->_prefix === null || $this->_prefix === '') {
-            $this->_prefix = 'launchdarkly';
+        /** @var ?string **/
+        $this->prefix = $options['redis_prefix'] ?? null;
+        if ($this->prefix === null || $this->prefix === '') {
+            $this->prefix = 'launchdarkly';
         }
 
+        /** @var ?Redis */
         $client = $this->_options['phpredis_client'] ?? null;
-        if ($client instanceof \Redis) {
-            $this->_redisInstance = $client;
+        if ($client instanceof Redis) {
+            $this->redisInstance = $client;
         } else {
-            $this->_redisOptions = [
+            $this->redisOptions = [
                 "timeout" => $options['redis_timeout'] ?? 5,
                 "host" => $options['redis_host'] ?? 'localhost',
                 "port" => $options['redis_port'] ?? 6379,
@@ -40,37 +40,34 @@ public function __construct($baseUri, $sdkKey, $options)
     protected function readItemString(string $namespace, string $key): ?string
     {
         $redis = $this->getConnection();
-        return $redis->hget("$this->_prefix:$namespace", $key);
+        return $redis->hget("$this->prefix:$namespace", $key);
     }
 
     protected function readItemStringList(string $namespace): ?array
     {
         $redis = $this->getConnection();
-        $raw = $redis->hgetall("$this->_prefix:$namespace");
+        $raw = $redis->hgetall("$this->prefix:$namespace");
         return $raw ? array_values($raw) : null;
     }
 
-    /**
-     * @return \Redis
-     */
-    protected function getConnection()
+    protected function getConnection(): Redis
     {
-        if ($this->_redisInstance instanceof \Redis) {
-            return $this->_redisInstance;
+        if ($this->redisInstance instanceof Redis) {
+            return $this->redisInstance;
         }
 
-        $redis = new \Redis();
+        $redis = new Redis();
         $redis->pconnect(
-            $this->_redisOptions["host"],
-            $this->_redisOptions["port"],
-            $this->_redisOptions["timeout"],
+            $this->redisOptions["host"],
+            $this->redisOptions["port"],
+            $this->redisOptions["timeout"],
             'launchdarkly/php-server-sdk-redis-phpredis'
         );
 
-        if ($this->_redisOptions['password']) {
-            $redis->auth($this->_redisOptions['password']);
+        if ($this->redisOptions['password']) {
+            $redis->auth($this->redisOptions['password']);
         }
 
-        return $this->_redisInstance = $redis;
+        return $this->redisInstance = $redis;
     }
 }
diff --git a/src/LaunchDarkly/Integrations/PHPRedis.php b/src/LaunchDarkly/Integrations/PHPRedis.php
index 919051d..547a896 100644
--- a/src/LaunchDarkly/Integrations/PHPRedis.php
+++ b/src/LaunchDarkly/Integrations/PHPRedis.php
@@ -1,4 +1,5 @@
 <?php
+
 namespace LaunchDarkly\Integrations;
 
 use LaunchDarkly\Impl\Integrations\PHPRedisFeatureRequester;
@@ -32,13 +33,13 @@ class PHPRedis
      *   - `apc_expiration`: expiration time in seconds for local caching, if `APCu` is installed
      * @return mixed  an object to be stored in the `feature_requester` configuration property
      */
-    public static function featureRequester($options = array())
+    public static function featureRequester($options = [])
     {
         if (!extension_loaded('redis')) {
             throw new \RuntimeException("phpredis extension is required to use Integrations\\PHPRedis");
         }
 
-        return function ($baseUri, $sdkKey, $baseOptions) use ($options) {
+        return function (string $baseUri, string $sdkKey, array $baseOptions) use ($options) {
             return new PHPRedisFeatureRequester($baseUri, $sdkKey, array_merge($baseOptions, $options));
         };
     }
diff --git a/tests/PHPRedisFeatureRequesterTest.php b/tests/PHPRedisFeatureRequesterTest.php
index 55199b5..65d730a 100644
--- a/tests/PHPRedisFeatureRequesterTest.php
+++ b/tests/PHPRedisFeatureRequesterTest.php
@@ -2,10 +2,8 @@
 
 namespace LaunchDarkly\Impl\Integrations\Tests;
 
-use LaunchDarkly\Impl\Integrations\PHPRedisFeatureRequester;
 use LaunchDarkly\Integrations\PHPRedis;
 use LaunchDarkly\SharedTest\DatabaseFeatureRequesterTestBase;
-use \Redis;
 
 class PHPRedisFeatureRequesterTest extends DatabaseFeatureRequesterTestBase
 {
diff --git a/tests/PHPRedisFeatureRequesterWithClientTest.php b/tests/PHPRedisFeatureRequesterWithClientTest.php
index add8e3a..a03186e 100644
--- a/tests/PHPRedisFeatureRequesterWithClientTest.php
+++ b/tests/PHPRedisFeatureRequesterWithClientTest.php
@@ -2,10 +2,10 @@
 
 namespace LaunchDarkly\Impl\Integrations\Tests;
 
+use \Redis;
 use LaunchDarkly\Impl\Integrations\PHPRedisFeatureRequester;
 use LaunchDarkly\Integrations\PHPRedis;
 use LaunchDarkly\SharedTest\DatabaseFeatureRequesterTestBase;
-use \Redis;
 
 class PHPRedisFeatureRequesterWithClientTest extends DatabaseFeatureRequesterTestBase
 {