Enable FILTER_FLAG_EMAIL_UNICODE for email format if present (jsonrainbow#398)

Author: erayd

src/JsonSchema/Constraints/FormatConstraint.php

@@ -124,7 +124,12 @@ public function check(&$element, $schema = null, JsonPointer $path = null, $i =
                 break;
 
             case 'email':
-                if (null === filter_var($element, FILTER_VALIDATE_EMAIL, FILTER_NULL_ON_FAILURE)) {
+                $filterFlags = FILTER_NULL_ON_FAILURE;
+                if (defined('FILTER_FLAG_EMAIL_UNICODE')) {
+                    // Only available from PHP >= 7.1.0, so ignore it for coverage checks
+                    $filterFlags |= constant('FILTER_FLAG_EMAIL_UNICODE'); // @codeCoverageIgnore
+                }
+                if (null === filter_var($element, FILTER_VALIDATE_EMAIL, $filterFlags)) {
                     $this->addError(ConstraintError::FORMAT_EMAIL(), $path, array('format' => $schema->format));
                 }
                 break;