Add PHP 8 Support (#4)

Signed-off-by: Lukas Kämmerling <lukas.kaemmerling@hetzner-cloud.de>

.github/workflows/tests.yml

@@ -9,7 +9,7 @@ jobs:
       fail-fast: true
       matrix:
         os: [ ubuntu-latest ]
-        php: [ 7.2, 7.3, 7.4 ]
+        php: [ 7.2, 7.3, 7.4, 8.0 ]
         dependency-version: [ prefer-lowest, prefer-stable ]
 
     name: P${{ matrix.php }} - ${{ matrix.dependency-version }} - ${{ matrix.os }}

composer.json

@@ -3,12 +3,12 @@
   "description": "Prometheus Push Gateway client for PHP applications.",
   "type": "library",
   "require": {
-    "php": "^7.2",
+    "php": "^7.2|^8.0",
     "guzzlehttp/guzzle": "^6.3|^7.0",
     "promphp/prometheus_client_php": "^1.0|^2.0"
   },
   "require-dev": {
-    "phpunit/phpunit": "^8.4",
+    "phpunit/phpunit": "^8.4|^9.4",
     "squizlabs/php_codesniffer": "^3.5",
     "phpstan/extension-installer": "^1.0",
     "phpstan/phpstan": "^0.12.50",