WordPress: Get page ID from slug

wp-get_id_by_slug

// Usage:
// get_id_by_slug('any-page-slug');

function get_id_by_slug($page_slug) {
	$page = get_page_by_path($page_slug);
	if ($page) {
		return $page->ID;
	} else {
		return null;
	}
}

// get the lastest post (this can also be used for custom post types through argument)
function get_latest_post()
{
    return get_posts('post_type=post&numberposts=1')[0];
}