Just started using Flex Framework with Eclipse Helios and find out how easy it is to develop flash based RIAs that run on flash player, something every developer should check and one interesting thing about it you can use it for desktop apps running it on AIR. So if u are a web developer with experience with PHP/MySQL and you want to develop not just web apps but all kind of apps, then I think you should checkt it out.

Flex is a highly productive, free, open source framework for building expressive web applications that deploy consistently on all major browsers, desktops, and operating systems by leveraging the Adobe® Flash® Player and Adobe AIR® runtimes. While Flex applications can be built using only the free Flex SDK, Adobe Flash Builder™ (formerly Adobe Flex® Builder™) software can accelerate development through features like intelligent coding, interactive step-through debugging, and visual design of the user interface layout.