Update php.yml

.github/workflows/php.yml

@@ -10,10 +10,10 @@ jobs:
   build:
       strategy:
         matrix:
-          php: ['5.6.40']
+          php: ['5.6']
           os: ['ubuntu-16.04']
           include:
-            - php: '5.6.40'
+            - php: '5.6'
               os: 'ubuntu-16.04'
     
       runs-on: ${{ matrix.os }}
@@ -30,9 +30,9 @@ jobs:
         uses: actions/cache@v2
         with:
           path: vendor
-          key: ${{ runner.os }}-php-${{ hashFiles('**/composer.lock') }}
+          key: ${{ matrix.os }}-php-${{ hashFiles('**/composer.lock') }}
           restore-keys: |
-            ${{ runner.os }}-php-
+            ${{ matrix.os }}-php-
 
       - name: Install dependencies
         if: steps.composer-cache.outputs.cache-hit != 'true'