MyBB

Hi!!
How are you?
I have a question,
I am creating a login box like vBulletin instead of mybb.quicklogin.
but I have a problem, How can I send current url to mybb login system (member.php)??? I added that code to my <form>::

<input type="hidden" name="url" value="{$redirect_url}" />

but it doesn't work ...
Any body can help me??
Thanks ..