Only run our PHPStan workflow if PHP files have changed. Also ensure we cache composer dependencies to make things faster

Author: dkotter

.github/workflows/phpstan.yml

@@ -5,12 +5,15 @@ on:
     branches:
       - develop
       - trunk
+    paths:
+      - "**.php"
   pull_request:
     branches:
       - develop
+    paths:
+      - "**.php"
 
 jobs:
-
   phpstan:
     name: PHPStan
     runs-on: ubuntu-latest
@@ -26,6 +29,19 @@ jobs:
           coverage: none
           tools: composer:v2
 
+      - name: Get composer cache directory
+        id: composer-cache
+        run: echo "dir=$(composer config cache-files-dir)" >> $GITHUB_OUTPUT
+
+      - name: Cache dependencies
+        id: cache-composer
+        uses: actions/cache@v4
+        env:
+          cache-name: cache-composer
+        with:
+          path: ${{ steps.composer-cache.outputs.dir }}
+          key: ${{ runner.os }}-build-${{ env.cache-name }}-${{ hashFiles('**/composer.lock') }}
+
       - name: Install dependencies
         run: composer install