Help with preg_replace

Hi I am having some problems with preg_replace and I wondering if someone could suggest a fix or explain why it is not working. Here is the Code: ********************* <?php $code = "blah http://www.foo.com/Unsubscribe.php?EmailAddress=[MAIL] blah"; $url = "'http://www.foo.com/maxbid/Unsubscribe.php?EmailAddress=[MAIL]'"; echo "BEFORE : $code<br><br>"; $replace = "Foo"; $code = preg_replace($url,$replace,$code,1); echo "AFTER: $code<br>"; ?> ********************** Here is the results of the script: ********************** BEFORE : blah http://www.qxlmaxbid.com/maxbid/Unsubscribe.php?EmailAddress=[MAIL] blah AFTER: blah http://www.qxlmaxbid.com/maxbid/Unsubscribe.php?EmailAddress=[MAIL] blah ********************** It should give the following result: ********************** AFTER: blah Foo blah ********************** Thanks for your help Regards John Clegg