switch_to_post() stack implementation (similar to switch_to_blog()) for WordPress

wp-switch-to-post.php

<?php

$WP_POST_STACK = array();

function switch_to_post($post_id) {
	global $WP_POST_STACK, $post;
	if (!count($WP_POST_STACK)) {
		$WP_POST_STACK[] = $post->ID;
	}
	$WP_POST_STACK[] = $post_id;
	$post = get_post($post_id);
	setup_postdata($post);
}

function restore_post() {
	global $WP_POST_STACK;
	if (count($WP_POST_STACK)) {
		$post_id = array_pop($WP_POST_STACK);
		$post = get_post($post_id);
		setup_postdata($post);
	}
}