In PHP, data that are sent via HTTP POST are in the following format:
variable1=data&variable2=dataThe data is immediately available via $_POST. Data that is sent via HTTP PUT is uploaded as a file to the server and must be parsed before reading. There's nothing wrong with it per se, except that writing data is inconsistent. There's no problem requiring my REST clients to upload a file using HTTP PUT, except that it's inconsistent.
So far, I used curl for testing my web app. I haven't tried sending data via <form> using a web browser, and I don't know whether <form method="put"> works. If it does, then the browser would probably send the data similar to POST's format, with only a different header (UPDATE - 2008/03/11: yepp, it indeed works that way). Blah, possibilities, possibilities.
I'm using Agavi framework, by the way. It's a kick-ass lightweight framework. Agavi is beautiful, but the documentation is sparse. Documentation effort is underway, and I hope to see more of it in the coming weeks. Without it, Agavi is considered "fringe" at the moment (I like fringe software; I even use fringe operating systems such as *BSD hehe).