groups_controller.php

<?php
class GroupsController extends AppController {
	var $name = 'Groups';
	var $paginate = array(
		'fields' => array(
			'Group.id',
			'Group.icon',
			'Group.name',
			'GroupCategory.name',
			'Group.location',
			'Group.description',
			'Group.website',
			'Group.created',
			'SUM(Donation.amount) AS donations',
		),
		'joins' => array(
			array(
				'table' => 'donations',
				'alias' => 'Donation',
				'type' => 'LEFT',
				'conditions' => array('Donation.group_id = Group.id'),
			),
		),
		'limit' => 8,
		'order' => array(
			'Group.name' => 'asc'
		),
		'group' => 'Group.id',
	);

	function admin_index() {
		if(!empty($this->data)) {
			$this->paginate['conditions'] = array(
				'MATCH (Group.name, Group.description) AGAINST (? IN BOOLEAN MODE)' => array($this->data['Group']['q'])
			);
		}
		$groups = $this->paginate('Group');
		$this->set(compact('groups'));
	}
}
?>

Please help! I am trying to have the donations column sortable, but visiting the url http://localhost/admin/groups/index/page:1/sort:donations/direction:asc does nothing. If I change the $paginate array to:

'order' => array(
    'donations' => 'desc'
),

the sort works, but after clicking on the sort tab (resulting in the url above) everything breaks.