Check if JSON_PRETTY_PRINT constant is defined instead of checking PHP version

Author: siwinski

bin/validate-json

@@ -218,7 +218,7 @@ $refResolver = new JsonSchema\RefResolver($retriever);
 $refResolver->resolve($schema, $urlSchema);
 
 if (isset($arOptions['--dump-schema'])) {
-    $options = version_compare(PHP_VERSION, '5.4.0', '>=') ? JSON_PRETTY_PRINT : 0;
+    $options = defined('JSON_PRETTY_PRINT') ? JSON_PRETTY_PRINT : 0;
     echo json_encode($schema, $options) . "\n";
     exit();
 }