Urgent :: How to redirect www.domain.com/forums to forums.domain.com

I want to redirect www.domain.com/forums to forums.domain.com and also dont want to lose my visitors from SE

i tries using

<?php
$URL="http://www.forums.mysite.com/";
header ("Location: $URL");
?> 

Code (markup):

but it just redirects www.domain.com/forums to forums.domain.com and not

www.mysite.com/forums/forumdisplay.php?f=2 to forums.mysite.com/forumdisplay.php?f=2

or

www.mysite.com/forums/showthread.php?t=2835 to
forums.mysite.com/showthread.php?t=2835

How do i get the later two working...

 

You should create .htaccess file and put there:
RewriteEngine On
RewriteRule ^/forums/(.*) http://forums.mysite.com/$1 [R,L]

 

Or you can use this php code:
<?php
$URL=preg_replace("/^\/forums\/(.+)/", "http://forums.mysite.com/$1", $_SERVER['REQUEST_URI']);
header ("Location: $URL");
?>

 

it easil as told by nikloas and u can also do it from c panel if u r using the cpanel

 

where and how to use this code plz help me i only know little abt php ot htaccess file