It's okay. WeBuilder 2006 is good as well, but it's not free. The best would be the Zend IDE, but that's like 400 bucks.
Honestly, the best program is one you feel comfortable working in. If you can't feel comfortable working in it, it's not for you.
But to learn PHP, you can't do that through a program. You need books, or tutorials to do that. The program is just an aide in getting you to the final project quicker so you don't have to constantly switch between windows to look up functions or get quick tips.