<?php
$this->Post->save(array(
	'Post' => array(
		'id' => 1,
	),
	'Tag' => array(
		'Tag' => array(2),
	),
));
// Foreward: Check out the debug SQL for this save ...
// DELETE FROM `posts_tags` WHERE post_id = '1'
// INSERT INTO `posts_tags` (post_id,tag_id) VALUES (1,2)
?>