ci: test against all LTS versions

Author: lgutschow

.github/workflows/ci.yml

@@ -1,15 +1,23 @@
 name: CI
+
 on:
-  push: { branches: [main] }
-  pull_request: { branches: [main] }
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
 jobs:
   test:
+    name: Test (PHP ${{ matrix.php-version }})
     runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        php-version: ["8.1", "8.2", "8.3", "8.4"]
     steps:
       - uses: actions/checkout@v6
       - uses: shivammathur/setup-php@v2
         with:
-          php-version: '8.3'
+          php-version: ${{ matrix.php-version }}
           extensions: gmp, openssl
       - run: composer install -q
       - run: vendor/bin/phpunit --colors=always