Hey does anyone know any method of making a PHP site secure. I mean though coding it and not the server setup. I have read up this topic on php.net and i was wondering if anyone here had discovered good methods of adding security to their site.

I ask this because a forum my friend set up, phpBB i think, someone used a crack or something to gain view all the users passwords. I want to be able to stop this happening though my own coding.

Thanks