Facebook IFrame and Ajax require_login()

Another day another bug (or just weird behavior) in Facebook platform.

When calling $facebook->require_login() from anywhere else then a canvas page it is caught in an endless loop.

I was going crazy over this for few days. The big problem was that conditions under which this error occurs distinguish between IE and FireFox.

In short - the solution is ... you have to carry Facebook signature variables (stored in $_GET) with you all the time.

$fbsig_vars = "";
$i=0;
foreach($_GET as $key => $value) {
 if (strpos($key,"fb_sig")!==false) {
 if ($i!=0) $fbsig_vars.= "&";
 $fbsig_vars.= "$key=$value";
 $i=1;
 }
}