Introduce PHPStan

Author: PowerKiKi

.travis.yml

@@ -13,6 +13,7 @@ before_script:
 script:
   - ./vendor/bin/php-cs-fixer fix --diff --verbose --dry-run
   - ./vendor/bin/phpunit --coverage-clover coverage-clover.xml
+  - ./vendor/bin/phpstan analyse -c phpstan.neon --level max src tests
 
 after_script:
   - wget https://scrutinizer-ci.com/ocular.phar && php ocular.phar code-coverage:upload --format=php-clover coverage-clover.xml

composer.json

@@ -6,7 +6,8 @@
     "scripts": {
         "check": [
             "php-cs-fixer fix --ansi --dry-run --diff",
-            "phpunit --color=always"
+            "phpunit --color=always",
+            "phpstan analyse -c phpstan.neon --level max src tests"
         ],
         "fix": [
             "php-cs-fixer fix --ansi"
@@ -30,7 +31,8 @@
     "require-dev": {
         "friendsofphp/php-cs-fixer": "^2.9",
         "zendframework/zend-diactoros": "^1.7",
-        "phpunit/phpunit": "@stable"
+        "phpunit/phpunit": "@stable",
+        "phpstan/phpstan": "^0.9.2"
     },
     "license": "MIT"
 }