строка состоящая из нескольких get параметров
$s = 'adfdf=1123&url=http://cs541207v4.vk.me/u63235608/videos/abbe4bbcd0.720.mp4?extra=qxzgmY36um2vOm3XmmutORuGfjwo__AWURSQcoEHnUn8BE54fPVJICkTDFpLfQ3SIdYn-nRUqjtlHo6R8brKHjZ3ChfTcY3x&c=3';
function parse($s)
{
$res = array();
foreach (explode('&',$s) as $tmp)
{
$tmp2 = explode('=',$tmp);
$key = $tmp2[0];
unset ($tmp2[0]);
$res[$key]=implode('=',$tmp2);
}
return $res;
}