regexp on user supplied link

Hi, I have a website which is based purely on user-added content. The problem with this is that some areas allow users to use links in the text, and it's difficult to ensure that they all have a decent knowledge of attributes such as tartget="_new", etc etc. So, I'd like a script that... 1. looks at $text for any link tags, and for each tag, does the following: 2. throws out everything except the HREF eg: <A HREF="http://www.somesite.com" target="_new">click</a> becomes http://www.somesite.com <A HREF="javascript:something();"> becomes javascript:something(); 3. prefixe the url with <A HREF=" 4. establish if it's an internal or external link: so how do we establish if it's an external link? well it'd be easy if we just say "anything begining with http:// is not relative", but because this content is user-driven, I'd like to be a little safer, and say "anything that begins with http://www.mysite.com OR http://mysite.com" is an external link. 5. if it's an external link, suffix the URL with " TARGET="_new">, or if it's internal, suffix it with "> Anyway, that'd be a great start. From there, I might like to prex each external link to go thru a program called out.php to log affiliate activity, and I might like to retain onmouseover, onclick, onmouseout etc etc properties in the tag, I might like to ensure a session ID is found within each internal link, and stripped from each external link, ensure that the <A> has a matching </A> etc etc, but the above would be a great start. Any help, especially with steps 1, 2 & 4, would be much appreciated. Thanks in advance, Justin French http://indent.com.au http://soundpimps.com