CakePHP Behavior that stops virtualFields from being selected unless they're explicitly requested.

lazy_virtual_fielder.php

<?php
/**
 * Behavior to stop CakePHP from including virtual fields unless they're
 * explicitly requested in the fields array.
 *
 * To find out more about virtual fields, consult the documentation in the
 * manual here:
 *
 * http://book.cakephp.org/view/1608/Virtual-fields
 *
 * @author joe bartlett (xo@jdbartlett.com)
 * @license http://www.opensource.org/licenses/mit-license.php MIT License
 * @package LazyVirtualFielderBehavior
 */
class LazyVirtualFielderBehavior extends ModelBehavior {

/**
 * After find callback. Wipes the model's virtual fields array for the next
 * query.
 *
 * @param object $model Model using this behavior
 * @access public
 */
	public function afterFind(&$Model) {
		$Model->virtualFields = array();
	}

/**
 * Runs before a Model::find() operation. Examines the query's requested
 * fields and tailors the model's ::virtualFields property appropriately.
 *
 * @param object $Model Model using this behavior
 * @param array $query Query parameters
 * @return bool TRUE
 * @access public
 */
	public function beforeFind(&$Model, $query) {
		if (empty($Model->lazyVirtualFields)) {
			$Model->lazyVirtualFields = $Model->virtualFields;
		}
		
		if (empty($Model->lazyVirtualFields)) {
			return TRUE;
		}
		
		$Model->virtualFields = array();
		
		$fields = (array)$query['fields'];
		foreach ($fields as $field) {
			if ($lazyVirtualField = $this->getLazyVirtualField($Model, $field)) {
				$Model->virtualFields += $lazyVirtualField;
			}
		}
		
		return TRUE;
	}

/**
 * Given a model and field name, returns an array representing a single
 * virtual field if one is found.
 *
 * @param object $Model Model using this behavior
 * @param string $field Name of a field being requested
 * @return mixed Boolean FALSE if nothing is found, array otherwise
 * @access public
 */
	public function getLazyVirtualField(&$Model, $field) {
		if (empty($Model->lazyVirtualFields) || !is_string($field)) {
			return FALSE;
		}
		
		if (isset($Model->lazyVirtualFields[$field])) {
			return array($field => $Model->lazyVirtualFields[$field]);
		}
		
		if (strpos($field, '.') !== FALSE) {
			list($model, $field) = explode('.', $field);
			if ($model == $Model->alias && isset($Model->lazyVirtualFields[$field])) {
				return array($field => $Model->lazyVirtualFields[$field]);
			}
		}
		
		return FALSE;
	}

}