PHP Intl extension has been added to default Yii requirements.

yii/requirements/requirements.php

@@ -2,6 +2,8 @@
 /**
  * This is the Yii core requirements for the [[YiiRequirementChecker]] instance.
  * These requirements are mandatory for any Yii application.
+ *
+ * @var $this YiiRequirementChecker
  */
 return array(
 	array(
@@ -36,4 +38,11 @@ return array(
 		'by' => '<a href="http://www.php.net/manual/en/book.mbstring.php">Multibyte string</a> processing',
 		'memo' => 'Required for multibyte encoding string processing.'
 	),
+	array(
+		'name' => 'Intl extension',
+		'mandatory' => true,
+		'condition' => $this->checkPhpExtensionVersion('intl', '1.0.2'),
+		'by' => '<a href="http://www.php.net/manual/en/book.intl.php">Internationalization</a> support',
+		'memo' => 'PHP Intl extension 1.0.2 or higher is required.'
+	),
 );