<?php 
class NullBehavior extends ModelBehavior {
    var $settings = array();

    /**
     * Enter description here...
     *
     * @param AppModel $model
     * @param unknown_type $config
     */
    function setup(&$model, $config = array() )
    {
        $this->settings[ $model->name ] = $config;
    }

    /**
     * Enter description here...
     *
     * @param AppModel $model
     */
    function beforeSave(&$model)
    {
        $config = $this->settings[$model->name];

        foreach ( $config AS $field )
        {
            if(
                true === array_key_exists($field,$model->data[$model->name] ) &&
                true === empty( $model->data[$model->name][$field] ) &&
                0 === strlen( $model->data[$model->name][$field] ) )
            {
                unset($model->data[$model->name][$field]);
            }
        }
        return true;
    }
}
?>