chore: adds phpstan workflow

Author: JasonTheAdams

.github/workflows/phpstan.yml

@@ -0,0 +1,35 @@
+name: 'PHPStan'
+on:
+  push:
+jobs:
+  phpstan:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout the repository
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 1
+      # ------------------------------------------------------------------------------
+      # Prepare our composer cache directory
+      # ------------------------------------------------------------------------------
+      - name: Get Composer Cache Directory
+        id: get-composer-cache-dir
+        run: |
+          echo "dir=$(composer config cache-files-dir)" >> $GITHUB_OUTPUT
+      - uses: actions/cache@v4
+        id: composer-cache
+        with:
+          path: ${{ steps.get-composer-cache-dir.outputs.dir }}
+          key: ${{ runner.os }}-composer-${{ hashFiles('**/composer.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-composer-
+      # ------------------------------------------------------------------------------
+      # Install dependencies
+      # ------------------------------------------------------------------------------
+      - name: Install dependencies
+        run: composer install --ignore-platform-reqs --no-interaction
+      # ------------------------------------------------------------------------------
+      # Run PHPStan
+      # ------------------------------------------------------------------------------
+      - name: Run PHPStan
+        run: composer phpstan