Raised minimum php version to 7.3

Updated phpunit version

Author: MaximilianKresse

composer.json

@@ -11,7 +11,7 @@
     ],
 
     "require": {
-        "php": "^7.2 || ^8.0",
+        "php": "^7.3 || ^8.0",
         "ext-pcre": "*",
         "ext-mbstring": "*",
 
@@ -20,7 +20,7 @@
     },
 
     "require-dev": {
-        "phpunit/phpunit": "^8.0",
+        "phpunit/phpunit": "^9.0",
         "php-defer/php-defer": "^4.0",
         "squizlabs/php_codesniffer": "^3.5",
         "phpstan/phpstan": "^0.12"