Prevent PHPStan installation for older php versions

Author: LeoColomb

.travis.yml

@@ -10,6 +10,9 @@ jobs:
     - php: 7.2
     - php: 7.3
     - php: 7.3
+      before_script:
+        - composer install
+        - composer require --dev phpstan/phpstan
       script: composer run analysis
     - php: nightly
 

composer.json

@@ -40,8 +40,7 @@
   },
   "require-dev": {
     "phpunit/phpunit": ">=4.0",
-    "squizlabs/php_codesniffer": "^3.0 || ^2.9.1",
-    "phpstan/phpstan": "^0.10.6"
+    "squizlabs/php_codesniffer": "^3.0 || ^2.9.1"
   },
   "autoload": {
     "psr-4": {