I’ve been using Zend Studio for many years now and think that it is a great IDE for building sites with PHP and JavaScript. IIRC I started with ZS 5; until this week I used version 9. I also ran a free Zend Server package, including Apache 2.2 and PHP 5.4. All this on an ordinary Windows 7 machine.
As my production web server now runs on Apache 2.4 and PHP 5.6, an upgrade on the dev machine seemed appropriate. Also, Zend recently launched Studio 13, with support for PHP 5.6 and even PHP 7. I decided to upgrade everything at once.