/**
* Stores the application instance in the class static member.
* This method helps implement a singleton pattern for CApplication.
* Repeated invocation of this method or the CApplication constructor
* will cause the throw of an exception.
* To retrieve the application instance, use {@link app()}.
* @param CApplication $app the application instance. If this is null, the existing
* application singleton will be removed.
* @throws CException if multiple application instances are registered.
*/
public static function setApplication($app)
{
if (self::$_app === null || $app === null) {
self::$_app = $app;
} else {
throw new CException(Yii::t('yii', 'Yii application can only be created once.'));
}
}