Recently Mike van Riel posted a review to his blog of an IDE that's growing in popularity - PHPStorm.

During my career as a PHP developer (hobbyist and professional) I have tried a multitude of IDEs and tools to write code in. Every IDE I have found thus far did great things but had their downsides. It is with phpStorm that I can send at least some of those problems to the past. [...] Having gotten that little push by MissYeh I decided to take a look at that new shiny IDE and found a true gem! phpStorm offers so much more than Netbeans and Eclipse in terms of performance, memory but also functionality.

He talks about some of his favorite features - native git support, a method usage search, more advanced docblock parsing and the ability to view "blame" information right in the IDE. He does note two things to keep an eye out for - the fact that it's still in beta and that, once it's fully released, it won't be free.