wp_nav_menu: show menu only if one exists, otherwise show nothing

Question

I'm trying to use wp_nav_menu to only display a menu if one exists, otherwise, display nothing.

If I delete the menu, it will output a list of the pages.

My functions.php file contains:

if (function_exists('register_nav_menus')) {
register_nav_menus (
array('main_nav' => 'Main Navigation Menu'));}

How can I use wp_nav_menu to only display a menu if one exists, otherwise show nothing?

Answer 1

Use has_nav_menu(), and test for theme_location, rather than menu_id:

<?php
if ( has_nav_menu( $theme_location ) ) {
    // User has assigned menu to this location;
    // output it
    wp_nav_menu( array( 
        'theme_location' => $theme_location, 
        'menu_class' => 'nav', 
        'container' => '' 
    ) );
}
?>

You can output alternate content, by adding an else clause.

EDIT

You need to replace $theme_location with your actual theme_location:

<?php
if ( has_nav_menu( 'main_nav' ) ) {
    // User has assigned menu to this location;
    // output it
    wp_nav_menu( array( 
        'theme_location' => 'main_nav', 
        'menu_class' => 'nav', 
        'container' => '' 
    ) );
}
?>

Answer 2

You can just specify false as the fallback_cb argument of wp_nav_menu. Nothing will show up -- rather, wp_nav_menu will return false (echoing nothing out).

<?php
wp_nav_menu(array( 
    'theme_location' => $main_nav, 
    'menu_class'     => 'nav', 
    'container'      => '',
    'fallback_cb'    => false
));

Answer 3

You can just register menu firstly without specifying the location.
In functions.php:

add_action( 'init', 'register_my_menus' );
function register_my_menus() {  
    register_nav_menus(
        array(
            'header' => __( 'Header Menu' )
        )
    );
}

And when you call the menu in header.php, check with has_nav_menu():

if ( has_nav_menu( 'header' ) ) {
    wp_nav_menu( array( 'theme_location' => 'header' ) ); 
}

Answer 4

Read this:

http://codex.wordpress.org/Function_Reference/wp_nav_menu

set 'fallback_cb' => false and none will be displayed, this is the standard method suggested by wp guys.