Add PHPStan in the Travis build

Author: Jean85

.travis.yml

@@ -30,9 +30,10 @@ jobs:
     - stage: Test
       php: 7.0
       env: COMPOSER_OPTIONS="--prefer-lowest"
-    - stage: codestyle
+    - stage: codestyle and SCA
       php: 7.1
       script: 
+        - vendor/bin/phpstan analyse src --level 7
         - vendor/bin/php-cs-fixer fix --verbose --diff --dry-run
     - stage: coverage
       php: 7.1

composer.json

@@ -31,8 +31,10 @@
     },
     "require-dev": {
         "friendsofphp/php-cs-fixer": "^2.5",
+        "phpstan/phpstan": "^0.8.4",
         "phpunit/phpunit": "^5.7|^6.0",
-        "scrutinizer/ocular": "^1.4"
+        "scrutinizer/ocular": "^1.4",
+        "symfony/expression-language": "^2.7|^2.8"
     },
     "autoload": {
         "psr-4" : {