[TASK] Run the unit tests with all supported PHP versions

Author: oliverklee

.github/workflows/ci.yml

@@ -41,7 +41,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        php-version: [ '5.6', '7.0', '7.1', '7.2', '7.3', '7.4' ]
+        php-version: [ '5.6', '7.0', '7.1', '7.2', '7.3', '7.4', '8.0', '8.1', '8.2', '8.3', '8.4' ]
 
     steps:
       - name: Checkout