[Validator] Added a check DNS option on URL validator

src/Symfony/Component/Validator/Constraints/Url.php

@@ -24,5 +24,7 @@ use Symfony\Component\Validator\Constraint;
 class Url extends Constraint
 {
     public $message = 'This value is not a valid URL.';
+    public $dnsMessage = 'The host could not be resolved.';
     public $protocols = array('http', 'https');
+    public $checkDNS = false;
 }

src/Symfony/Component/Validator/Constraints/UrlValidator.php

@@ -62,6 +62,18 @@ class UrlValidator extends ConstraintValidator
             $this->buildViolation($constraint->message)
                 ->setParameter('{{ value }}', $this->formatValue($value))
                 ->addViolation();
+
+            return;
+        }
+
+        if ($constraint->checkDNS) {
+            $host = parse_url($value, PHP_URL_HOST);
+
+            if (!checkdnsrr($host, 'ANY')) {
+                $this->buildViolation($constraint->dnsMessage)
+                   ->setParameter('{{ value }}', $this->formatValue($host))
+                   ->addViolation();
+            }
         }
     }
 }

src/Symfony/Component/Validator/Resources/translations/validators.en.xlf

@@ -302,6 +302,10 @@
                 <source>An empty file is not allowed.</source>
                 <target>An empty file is not allowed.</target>
             </trans-unit>
+            <trans-unit id="79">
+                <source>The host could not be resolved.</source>
+                <target>The host could not be resolved.</target>
+            </trans-unit>
         </body>
     </file>
 </xliff>

src/Symfony/Component/Validator/Resources/translations/validators.fr.xlf

@@ -302,6 +302,10 @@
                 <source>An empty file is not allowed.</source>
                 <target>Un fichier vide n'est pas autorisé.</target>
             </trans-unit>
+            <trans-unit id="79">
+                <source>The host could not be resolved.</source>
+                <target>Le nom de domaine n'a pas pu être résolu.</target>
+            </trans-unit>
         </body>
     </file>
 </xliff>