Search a string between <foo></foo>

Hi... I have a text and, some words of the text have the tags <url></url> between them. What i'm trying to do is to replace the word between that tags for a url, wich I'll search them in a database and convert to a url. It's working fine when I have only one <url></url>, but when there are more than one, the script converts all the text between the first <foo></foo> and the last <foo></foo>. I'm using this code: if (eregi("<foo>(.*)</foo>", $string, $result)) { $string = str_replace($result[1], '<a href="'.$result[1].'">'.$result[1].'</a>', $string); } Someone knows what I have to do to put it to work??? Thanks in advance. Luiz Vitor Brazil