Nusphere PHPEd. That's the one I use after horrible Java based alternatives and Zend Studio to name the waterheaded ones :P. It's blazing fast, has built in code completion library, fully customizable syntax highlighting for PHP 4.x, PHP 5.x, PHP 5.3, html, css, smarty, perl, sql, xml, c/c++, python, asp, js and who knows what else.
Highlights:
- Über fast development environment.
- Awesome file manager options (SFTP, SSH, etc.)
- Fully customizable syntax highlighting (light/dark profiles)
- Built in debugger
- Fully customizable editor options (brackets, completion, whatever...)