I am implementing a Proxy.api function in my store but cannot seem to access the parameters once they are passed to the .php files. The store is connected to a form.Panel and when I click "Create" on the form I want the form elements to be sent to a .php file to be stored in a MYSQL database.

Here is the proxy with api configuration:
var store = Ext.create('Ext.data.Store', {
        //connect it to the person model
        model: 'User',
        autoLoad: true,
        autoSync: true,
        //set up the proxy to communicate the data
        proxy: {
            type: 'ajax',
            api: {
                read: 'u_read.php',
                create: 'u_create.php',
                update: 'u_update.php',
                destroy: 'u_update.php'
            //create a reader to read from the database to the store
            reader: {
                type: 'json',
                successProperty: 'success',
                root: 'data',
                messageProperty: 'message'
I can see in FireBug that the 'create' command is executed correctly when I click the "CREATE" button in my application, and it correctly POSTs the 'data' json object:

but in the .php file I cannot access the 'data' json object or its contents.
This is what I have in u_create.php:
        //get passed parameters
        $data = $_POST[data];
        $email = $data['email'];
        $first = $data['first'];
        $last = $data['last'];
        $response = array();
        $response['success'] = true;
        $response['message'] = "Created User";
        $response['data'] = array(
            'first' => $first, 
            'last' => $last,
            'email' => $email);
        return json_encode($response);
but the application doesn't return the $response json packet - it returns '0' and a 'result is undefined' error

How can I access the POSTed arguments sent to my .php file from the proxy.api?

Thanks in advance!