add matrix correctly

Author: nicklog

.github/workflows/php.yml

@@ -3,10 +3,10 @@ name: PHP Composer
 on:
   push:
     branches:
-    - master
+      - master
   pull_request:
     branches:
-    - master
+      - master
 
 jobs:
   build:
@@ -20,6 +20,11 @@ jobs:
     steps:
     - uses: actions/checkout@v2
 
+    - name: Install PHP
+      uses: shivammathur/setup-php@v2
+      with:
+        php-version: ${{ matrix.php-versions }}
+
     - name: Validate composer.json and composer.lock
       run: composer validate