Fix static analysis on Travis.

.travis.yml

@@ -74,6 +74,10 @@ install:
   - composer self-update
   # Install Composer packages.
   - composer install
+  # PHPStan
+  - if [ "$PHPSTAN" == "1" ]; then composer bin phpstan install; fi
+  # Psalm
+  - if [ "$PSALM" == "1" ]; then composer bin psalm install; fi
   # Test on specific WordPress version.
   - composer require --dev --update-with-dependencies roots/wordpress:${WP_VERSION} wp-phpunit/wp-phpunit:${WP_VERSION}
   # List available packages.
@@ -89,9 +93,9 @@ script:
   # PHP Mess Detector
   - if [ "$PHPMD" == "1" ]; then composer run-script phpmd; fi
   # PHPStan
-  - if [ "$PHPSTAN" == "1" ]; then phpstan analyze; fi
+  - if [ "$PHPSTAN" == "1" ]; then composer run-script phpstan; fi
   # Psalm
-  - if [ "$PSALM" == "1" ]; then psalm; fi
+  - if [ "$PSALM" == "1" ]; then composer run-script psalm; fi
 
 after_success:
   - if [ "$COVERAGE" == "1" ]; then composer run-script coveralls; fi