I'm trying to set up a header redirect to a mobile version of a site using the Mobile_Detect.php class.

I've got it working fine as a standard redirect to the main page, but I'd like it to incorporate the user's menu choice, and take them straight to the relevant page on the mobile version, by appending the value of $_GET to the redirect address string.

My code is:
$mob_link = 'Location: mobile/christmas2012m.php';
		if ($_GET['p']) $mob_link = $mob_link + '?p=' + $_GET['p'];
		header($mob_link, true, 301);
Unfortunately if $_GET['p'] has a value, I get a 'Moved Permanently' page error. Any thoughts about why this is?