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I've used PHP for about 5 years - very solid, and was able to do a lot with it. Mostly db-backed web sites.
But it's a pain to make "CRUD" style applications - edit, update, delete data. I've been playing with Ruby on Rails since last December, and it is leaps and bounds ahead of Php. It is extraordinarily easy to build db apps with it.
I got a book on building PHP e-commerce sites last winter. It is very well done, and the code was factored out into the proper MVC components. And it was enormous - a ton of code to do updates, to handle grids. It just wasn't worth it to implement for me. Rails literally cut the code from the book by 80%, while maintaining the MVC framework. Books are already coming out for Rails, so check them out and compare to php...