lint all files with GitHub Actions

Author: xabbuh

.github/workflows/ci.yaml

@@ -0,0 +1,49 @@
+name: 'CI'
+
+on:
+  - 'push'
+  - 'pull_request'
+
+jobs:
+  tests:
+    name: 'Lint files'
+
+    runs-on: 'ubuntu-latest'
+
+    strategy:
+      matrix:
+        php-version:
+          - '5.3'
+          - '5.4'
+          - '5.5'
+          - '5.6'
+          - '7.0'
+          - '7.1'
+          - '7.2'
+          - '7.3'
+          - '7.4'
+          - '8.0'
+
+    steps:
+      - name: 'Check out'
+        uses: 'actions/checkout@v2'
+
+      - name: 'Set up PHP'
+        uses: 'shivammathur/setup-php@v2'
+        with:
+          php-version: '${{ matrix.php-version }}'
+          coverage: 'none'
+
+      - name: 'Get Composer cache directory'
+        id: 'composer-cache'
+        run: 'echo "::set-output name=cache-dir::$(composer config cache-files-dir)"'
+
+      - name: 'Cache dependencies'
+        uses: 'actions/cache@v2'
+        with:
+          path: '${{ steps.composer-cache.outputs.cache-dir }}'
+          key: "php-${{ matrix.php-version }}-composer-locked-${{ hashFiles('composer.lock') }}"
+          restore-keys: 'php-${{ matrix.php-version }}-composer-locked-'
+
+      - name: 'Lint PHP files'
+        run: 'find src -type f -name "*.php" -exec php -l {} \; | (! grep -v "No syntax errors detected" )'