How to use logout function on custom menu link?

All

I am using wordpress custom menu, and there is one menu as Logout.
I know wordpress Logout function <?php echo wp_logout_url(); ?>

But how can i use it in custom menu ?

Not sure how and where you can create a custom button, but you can add such a link per filter: Add a filter function to 'wp_nav_menu_objects' and insert the link where you need it.

Here is a basic example:

add_filter( 'wp_nav_menu_objects', 'wpse_46547_add_log_out_link', 10, 2 );

function wpse_46547_add_log_out_link( $sorted_menu_items, $args )
{
    $link = array (
        'title'            => 'Log out',
        'menu_item_parent' => 0,
        'ID'               => '',
        'db_id'            => '',
        'url'              => wp_logout_url()
    );

    $sorted_menu_items[] = (object) $link;

    return $sorted_menu_items;
}

You should modify the code:

• Check if you are on the correct menu. For example require a class has_log_out_link for the menu_class parameter on wp_nav_menu and test $args->menu_class.
• I18n for the menu title. 😉
• Set menu_item_parent to a post ID other than 0 if you need the link in a sub menu.
• There are more parameters for the link, see my other answer to inspect those.