One of the few Editors with full PHP 5 support, EngInSite Editor for PHP is a complete integrated development environment(IDE) for creating, testing and debugging PHP scripts, which runs on Windows 9x/NT/2000/XP or later.

By bringing together the editing, testing and debugging instruments into a single, easy-to-use, user-oriented environment, EngInSite Editor for PHP enables you to develop PHP applications on your desktop.

http://www.enginsite.com/php-editor.htm