quite easy, the function is called parse_str(), and its even cool:
parse_str($url_string); returns it as variables
second parameter:
parse_str($url_string,$array)
returns it into an acssiociative array.
so, example:
$url_string = "index.php?id=10&name=peter";
parse_str($url_string);
now the variables
$id = 10
and $name = "peter" are aviable
parse_str($url_string,$array);
$array["id"] = 10;
$array["name"] = "peter";