Regular expressions prob..

I am building a comment script, and want to parse special codes:

[a]http://url[/a] and
[a url="http://url"]description[/a]

well, i gots it working, but when this code is used in a post multiple times, it goes all goofy. like <a href="url">[/a]

the regular expressions I use are:

$comments = eregi_replace("[a url="(.*)"](.*)[/a]", "<a href="1">2</a>", $comments);
$comments = eregi_replace("[a](.*)[/a]", "<a href="1">1</a>", $comments);

Any ideas how to fix this?

Thanks.

[This message has been edited by Fquist (edited May 17, 2000).]

[This message has been edited by Fquist (edited May 17, 2000).]

Anyone? =P