Regular Expressions and urls

I am trying to find a regex to relace a url in text with the <a href=... to make it a link. The urls in the text are sometimes enclosed in () or [] Here is what I have now: function make_url($txt){ return eregi_replace("((ftp://)|(http://)|(www))(([a-z0-9.\-])*)(@)?(([a-z0-9\.])*) (([:/])?)((([a-z0-9]*)(@?)/*)+([.a-z]{2,4}){1})?((\??[a-z0-9\=]*)?)((\&[a-z0 -9\=]*)?)(([\.a-z]){2,4})?", "<a href=\"\\0\" target=\"_blank\">\\0</a>",$txt); } This works, except in some cases, like the following urls, the end path is left off. [http://www.geocities.com/Heartland/5792/] [http://www.iidc.indiana.edu/~irca/] Does anyone have something that will work with all urls?