<?php

$string = 'http://example.com/profile.php?id=9999&refid=22';

$url = parse_url($string);

parse_str($url['query'], $get);

unset($get['refid']);

$url['query'] = http_build_query($get);

echo $url['scheme'] . '://' . $url['host'] . $url['path'] . '?' . $url['query'];

http://example.com/profile.php?id=9999