This is my parser file...
<?php
//it grabs the init file, wherever it is located relative to the parser file itself
require_once '../users/init.php';
//it instantiates the DB
$db = DB::getInstance();

//in this example I am getting users to sign up for a certain task, so it is looking for the id of the task and the id of the user, which I passed to it from jquery.
$task_id = Input::get('task_id');
$checked = Input::get('checked');
$user_id = ($checked)?$user->data()->id : 0;
$username = $user->fullName(); // this is a custom function, but essentially it is the user's first/last name

//then the db is updated
$db->update('kitchen_tasks',$task_id,['user'=>$user_id]);

//a response is sent
$response = ['success'=>true,'user_name'=>$username,'task_id'=>$task_id,'checked'=>$checked];
echo json_encode($response);
die;

HERE is my javascript at the bottom of my userspice page... Most of the count stuff on the page is not important. It's just showing how many boxes are checked.
<script>

	function handleTaskCheck(evt){
		// data-* attributes are accessed by evt.target.dataset.*
		if(evt.target.checked === true){
			taskCount++;
		} else {
			taskCount--;
		}

		jQuery.ajax({
			url:"parsers/kitchen_tasks.php",
			method:"POST",
			data:{task_id:evt.target.dataset.id,checked:evt.target.checked},
			success: taskUpdateSuccess
		});

		jQuery('#taskCount').html(taskCount);
	}

	function taskUpdateSuccess(resp){
		var r = JSON.parse(resp);
		if(r.success){
			if(r.checked === "true"){
				jQuery('#assignedUser_'+r.task_id).html(" "+r.user_name);
			} else {
				jQuery('#assignedUser_'+r.task_id).html("");
			}
		}
	}

</script>