You can also use one of the RESTful PHP micro-frameworks. Slim in particular has good support for all the HTTP methods. I blogged a sample app here: http://coenraets.org/blog/2011/12/restful-services-with-jquery-php-and-the-slim-framework/. In this example, I send a JSON string when sending a PUT request. The JSON string is available using the getBody() method of Slim's request object. But you can also "PUT" url encoded form params in which case you can access them like this at the server side:
$paramValue = $app->request()->put('paramName');