There are many discussions of editors and IDE's in these boards. It tends to become a "religious flame war" at times ... well, kinda, anyway. I'd look them up, and use your search engine of choice ... install a few, and use what you like.
Choice would be depending on your OS, personal preferences, hardware power, and workflow/business processing needs.
Here's a list of some of the IDE's and editors available:
IDE's: Komodo, NetBeans, Zend Studio, Aptana, Eclipse, PHPStorm, Nusphere ...
I use NetBeans, but it's RAM-intensive.
Smaller "Featureful" Editors: SciTE, Komodo Edit, CodeLobster, TextWranger, Notepad++, gVim, PSPad ... there are dozens.
I use Notepad++.
Very Small/CLI Editors: Notepad, vi, pico, kate, nano, ed(1) ... 😛
I can use vi, but I generally install nano on a server if I can.
HTH,