get url /link from a sring

[vivek avasthi]

how to get url & link from a string :

example :

$str="the lis is aponsored by <a href="sitename/filename>link.php</a> sdgsd dfbvgdfbd dfzvgdfvgsdb <a href="sitename/filename>link.php</a> vbsdfbvgsdvgfsdvgsdgsdfsdfsdfasdfsdfsdffdsg <a href="sitename/filename>link.php</a> ";.

now i want to extarct only link/url from the string.

[jatar_k]

I found this thread that might help
[webmasterworld.com...]