refactor conditional logic of 'required' validation

Author: alexmmm

src/JsonSchema/Constraints/Undefined.php

@@ -109,20 +109,20 @@ protected function validateCommonProperties($value, $schema = null, $path = null
 
         // Verify required values
         if (is_object($value)) {
-            if ($value instanceof Undefined) {
-                // Draft 3 - Required attribute - e.g. "foo": {"type": "string", "required": true}
-                if (isset($schema->required) && $schema->required) {
-                    $this->addError($path, "is missing and it is required");
+            if (isset($schema->required) && is_array($schema->required) ) {
+                // Draft 4 - Required is an array of strings - e.g. "required": ["foo", ...]
+                foreach ($schema->required as $required) {
+                    if (!property_exists($value, $required)) {
+                        $this->addError($path, "the property " . $required . " is required");
+                    }
                 }
             } else if (isset($schema->required)) {
-                if( is_array($schema->required)) {
-                    // Draft 4 - Required is an array of strings - e.g. "required": ["foo", ...]
-                    foreach ($schema->required as $required) {
-                        if (!property_exists($value, $required)) {
-                            $this->addError($path, "the property " . $required . " is required");
-                        }
-                    }
+                // Draft 3 - Required attribute - e.g. "foo": {"type": "string", "required": true}
+                if ( $schema->required && $value instanceof Undefined) {
+                    $this->addError($path, "is missing and it is required");
                 }
+            } else if ($value instanceof Undefined) {
+                // don't check type of Undefined value
             } else {
                 $this->checkType($value, $schema, $path);
             }