Add PHPStan static analysis at level 0

.github/workflows/ci.yml

@@ -43,6 +43,41 @@ jobs:
       - name: Run build
         run: npm run build
 
+  phpstan:
+    name: PHPStan
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Setup PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: '8.3'
+
+      - name: Cache Composer
+        uses: actions/cache@v4
+        with:
+          path: ~/.composer/cache
+          key: ${{ runner.os }}-composer-phpstan-${{ hashFiles('**/composer.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-composer-phpstan-
+
+      - name: Install Composer dependencies
+        run: composer install --no-interaction --no-progress
+
+      - name: Cache PHPStan result cache
+        uses: actions/cache@v4
+        with:
+          path: .phpstan-cache
+          key: ${{ runner.os }}-phpstan-${{ hashFiles('**/composer.lock', 'phpstan.neon.dist') }}-${{ github.sha }}
+          restore-keys: |
+            ${{ runner.os }}-phpstan-${{ hashFiles('**/composer.lock', 'phpstan.neon.dist') }}-
+            ${{ runner.os }}-phpstan-
+
+      - name: Run PHPStan
+        run: composer phpstan
+
   e2e:
     name: E2E (Playwright)
     runs-on: ubuntu-latest

.gitignore

@@ -58,3 +58,6 @@ package/dist
 
 # AI generated files
 .claude/
+
+# PHPStan result cache
+/.phpstan-cache/

composer.json

@@ -11,7 +11,11 @@
     "phpcompatibility/phpcompatibility-wp": "dev-master",
     "phpcompatibility/php-compatibility": "dev-develop as 9.99.99",
     "automattic/vipwpcs": "^3.0",
-    "wp-coding-standards/wpcs": "^3.0"
+    "wp-coding-standards/wpcs": "^3.0",
+    "phpstan/phpstan": "^2.0",
+    "szepeviktor/phpstan-wordpress": "^2.0",
+    "php-stubs/wp-cli-stubs": "^2.10",
+    "php-stubs/woocommerce-stubs": "^9.0"
   },
   "config": {
     "platform": {
@@ -27,6 +31,9 @@
     ],
     "fix": [
       "phpcbf"
+    ],
+    "phpstan": [
+      "phpstan analyse --memory-limit=-1"
     ]
   },
   "minimum-stability": "dev"