This is a very rich IDE (integrated development environment) for PHP. We used it a little bit, but we got our (beta) copy after we had become comfortable with simpler editors. Our projects were small, single-file experiments. If we were beginning a larger PHP project, this tool would probably be at the heart. In that case, the productivity payback for the considerable installation effort and the light learning curve would probably be pretty quick.
Zend.com The commercial arm of the PHP's hardworking mentors.
PHPBuilder.com An independent development oriented site with great community.