feat: re-add caching command, add linting command

.github/workflows/php.yml

@@ -17,20 +17,21 @@ jobs:
     - name: Validate composer.json and composer.lock
       run: composer validate --strict
 
-      #    - name: Cache Composer packages
-      #id: composer-cache
-      #uses: actions/cache@v2
-      #with:
-      #  path: vendor
-      #  key: ${{ runner.os }}-php-${{ hashFiles('**/composer.lock') }}
-      #  restore-keys: |
-      #    ${{ runner.os }}-php-
+    - name: Cache Composer packages
+      id: composer-cache
+      uses: actions/cache@v2
+      with:
+        path: vendor
+        key: ${{ runner.os }}-php-${{ hashFiles('**/composer.lock') }}
+        restore-keys: |
+          ${{ runner.os }}-php-
 
     - name: Install dependencies
       run: composer install --prefer-dist --no-progress --ignore-platform-reqs
 
-    # Add a test script to composer.json, for instance: "test": "vendor/bin/phpunit"
-    # Docs: https://getcomposer.org/doc/articles/scripts.md
+    - name: Lint PHP code
+      run: composer run lint:php
 
+    # TODO: Add tests
     # - name: Run test suite
     #   run: composer run-script test