I need to pass the value of an element to an $ajax->link without using a form/submit structure. (because I have a dynamically set number of clickable links through which I am triggering the action)

I used to do this in Ruby using the Prototype javascript function $F like this:

<%= link_to_remote "#{item.to_s}", 
     :url => { :action => :add_mpc }, 
     :with => "'category=' + $F('mpc_category')" -%>

But this does not seem to work in Cakephp:

<?php echo $ajax->link(substr($vehicle['vehicles']['year'], -2), 
      array('action' => 'add_mpc', 'category' => '$F("mpc_category")'),
      array('update' => 'results', 'position' => 'top')); ?>

PHP sees $F as a variable instead of a call to javascript. I'm not too familiar with Javascript, but is there another way to pass the value of the 'mpc_category' input element to the controller through this link? I have been looking for a couple days and can't find anyone dealing with this specific issue. Thanks for any assistance.

Edit: fixed syntax in php statement.