hello... you have several options to implement this. use preg_replace function or use parse_url function. below i have explained it further.
$tempText = "hello.. how are you?? are you keeping well?? please checkout this url http://www.youtube.com/watch?v=ehuwoGVLyhg&feature=topvideos";
print_r(parse_url($tempText,PHP_URL_PATH));
hope this would be useful.
Thanks!
Asoka