Adding 'setup-php' plugin

Fixing broken php version pointer

Author: danny-gallagher

.github/workflows/test.yml

@@ -18,6 +18,12 @@ jobs:
 
     steps:
     - uses: actions/checkout@v2
+      
+    - name: Install PHP
+      uses: shivammathur/setup-php@v2
+      with:
+        php-version: ${{ matrix.php }}
+        coverage: none
 
     - name: Install dependencies
       run: |