Add stricter rule for phpstan

composer.json

@@ -119,7 +119,7 @@
         ],
         "tests": "php ./vendor/bin/phpunit",
         "phpcs": "php ./vendor/bin/phpcs src/ tests/",
-        "phpstan": "php -d memory_limit=4G vendor/bin/phpstan analyse src/ tests/unit/ tests/functional/",
+        "phpstan": "php -d memory_limit=4G vendor/bin/phpstan analyse src/ tests/unit/ tests/functional/ -l 8",
         "php-cs-fixer": "tools/php-cs-fixer/vendor/bin/php-cs-fixer fix src/ tests/unit/ tests/functional/"
     },
     "conflict": {