I was wondering if anyone could help out.
I want to create a script which acts in a way similar to BBcode.
In a user-editable text-box, users would be able to write thinks like:

[link url="http://www.sitepoint.com"]Go To Sitepoint[/link]
I want to change this into the form of:

Code HTML4Strict:
<a href="http://www.sitepoint.com">Go To Sitepoint</a>

I think PHP's str_replace() function would be the correct method, but I just can't figure out how I would use is.
I know that I could just use BBcode but i would like to be able to make this from scratch, as it needs some unique features.
Any help on how I would do this would be appreciated.