Also test on PHP 8.1

Author: PowerKiKi

.github/workflows/php.yml

@@ -68,7 +68,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        php: ['7.1', '7.2', '7.3', '7.4', '8.0'] #, '8.1'
+        php: ['7.1', '7.2', '7.3', '7.4', '8.0', '8.1']
     steps:
       -   name: Setup PHP
           uses: shivammathur/setup-php@v2