I have an interactive web application powered by jQuery where users can manipulate visual objects on the screen. When done, the \"state\" of JavaScript objects should be sent to
json_decode() should serve you well here.
If you simply append a string containing the JSON representation of your javascript object to your HTTP request, you can json_decode() it in PHP and have a PHP object ready to go.
Edit: I should mention that this page has a link to a Javascript JSON stringifier, which will convert your JS objects into the necessary JSON.