The NetBeans team (Sun) has recently announced namspace support or PHP development in their IDE. They've also just posted a screencast showing how this new functionality works.
We've now finished a screencast demonstrating PHP 5.3 namespace support in NetBeans IDE 6.8. (See Code Completion for Namespaces part I). The screencast also shows code hints for assigning variables, namespace naming hints, and how to set the options for PHP code completion.