diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index 1e56444..6d3c219 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -25,3 +25,5 @@ jobs:
               run: vendor/bin/phpunit
             - name: Check Code Styles
               run: vendor/bin/ecs
+            - name: Check PHPStan
+              run: vendor/bin/phpstan analyze src tests --level 5
diff --git a/Makefile b/Makefile
index fd24f70..0c05564 100644
--- a/Makefile
+++ b/Makefile
@@ -29,4 +29,11 @@ install:
 ecs:
 	vendor/bin/ecs --fix
 
+## run tests
+test:
+	vendor/bin/phpunit
+
+## run phpstan
+phpstan:
+	vendor/bin/phpstan analyze src tests --level 5
 
diff --git a/composer.json b/composer.json
index d6e448c..a2b2e03 100644
--- a/composer.json
+++ b/composer.json
@@ -14,7 +14,11 @@
     },
     "require-dev": {
         "whatwedo/php-coding-standard": "^1.0",
-        "phpunit/phpunit": "^9.5"
+        "phpunit/phpunit": "^9.5",
+        "phpstan/phpstan": "^1.10",
+        "symfony/http-kernel": "^7.0",
+        "symfony/dependency-injection": "^7.0",
+        "symfony/config": "^7.0"
     },
     "autoload": {
         "psr-4": {
diff --git a/phpstan.neon b/phpstan.neon
new file mode 100644
index 0000000..31f6166
--- /dev/null
+++ b/phpstan.neon
@@ -0,0 +1,5 @@
+parameters:
+    level: 1
+    paths:
+        - src
+        - tests
diff --git a/src/DependencyInjection/whatwedoTwigBootstrapIconsExtension.php b/src/DependencyInjection/whatwedoTwigBootstrapIconsExtension.php
index dbf34e2..116a10c 100644
--- a/src/DependencyInjection/whatwedoTwigBootstrapIconsExtension.php
+++ b/src/DependencyInjection/whatwedoTwigBootstrapIconsExtension.php
@@ -11,9 +11,9 @@
 
 class whatwedoTwigBootstrapIconsExtension extends Extension
 {
-    public function load(array $configs, ContainerBuilder $container)
+    public function load(array $configs, ContainerBuilder $container): void
     {
-        $loader = new PhpFileLoader($container, new FileLocator(\dirname(__DIR__) . '/Resources/config'));
+        $loader = new PhpFileLoader($container, new FileLocator(\dirname(__DIR__).'/Resources/config'));
         $loader->load('config.php');
     }
 }
diff --git a/src/Twig/BootstrapIconsExtensions.php b/src/Twig/BootstrapIconsExtensions.php
index 8360022..7af93d2 100644
--- a/src/Twig/BootstrapIconsExtensions.php
+++ b/src/Twig/BootstrapIconsExtensions.php
@@ -15,7 +15,7 @@ class BootstrapIconsExtensions extends AbstractExtension
     /**
      * @return TwigFunction[]
      */
-    public function getFunctions()
+    public function getFunctions(): array
     {
         return [
             new TwigFunction('bootstrap_icon', [$this, 'getIcon'], [
@@ -33,12 +33,12 @@ public function getIcon(string $icon, array $attributes = [])
         }
 
         array_walk($attributes, static function (&$val, $key) {
-            $val = $key . '="' . $val . '" ';
+            $val = $key.'="'.$val.'" ';
         });
 
         return str_replace(
             '<svg ',
-            '<svg ' . implode(' ', $attributes),
+            '<svg '.implode(' ', $attributes),
             preg_replace('/class=".*?"/', '', file_get_contents($iconPath))
         );
     }
@@ -50,9 +50,9 @@ protected function getIconsPath(): string
         }
 
         foreach (ClassLoader::getRegisteredLoaders() as $vendorDir => $loader) {
-            $installed = require $vendorDir . '/composer/installed.php';
+            $installed = require $vendorDir.'/composer/installed.php';
             if (isset($installed['versions']['twbs/bootstrap-icons'])) {
-                return static::$iconsPath = $vendorDir . '/twbs/bootstrap-icons';
+                return static::$iconsPath = $vendorDir.'/twbs/bootstrap-icons';
             }
         }