Update php.yml

Author: lewisgoddard

.github/workflows/php.yml

@@ -13,7 +13,7 @@ jobs:
   build:
     strategy:
       matrix:
-        php-version: [ "8.3", "8.2" ]
+        php-version: [ "8.3", "8.2", "8.1" ]
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v4