Custom nav menu not showing

Question

I want to make a custom menu that will be a select-box,

I registered a custom menu:

add_action( 'init', 'register_my_menu' );

function register_my_menu() {
    register_nav_menu( 'primary', 'Primary Menu' );
}

I added a custom menu crawler to the heading using this: How to use wp_nav_menu to create a select menu dropdown?

    <nav class="page-name">
        <?php
            class Walker_Nav_Menu_Dropdown extends Walker_Nav_Menu{
                function start_lvl(&$output, $depth){
                    $indent = str_repeat("\t", $depth); // don't output children opening tag (`<ul>`)
                }

                function end_lvl(&$output, $depth){
                    $indent = str_repeat("\t", $depth); // don't output children closing tag
                }

                function start_el(&$output, $item, $depth, $args){ // add spacing to the title based on the depth
                    $item->title = str_repeat("&nbsp;", $depth * 2).$item->title;

                    parent::start_el(&$output, $item, $depth, $args);

                    // no point redefining this method too, we just replace the li tag...
                    $output = str_replace('<li', '<option', $output);
                }

                function end_el(&$output, $item, $depth){
                    $output .= "</option>\n"; // replace closing </li> with the option tag
                }
            }

            wp_nav_menu(array(
                'theme_location' => 'primary', // your theme location here
                'walker'         => new Walker_Nav_Menu_Dropdown(),
                'items_wrap'     => '<select>%3$s</select>',
            ));
        ?>
    </nav>

And created a custom menu in the WP-Admin

But still the menu doesn't show. What am I missing?

Update
Apparently The crawler function does make an output but it is messed up,
When I use just register_nav_menu( 'primary', 'Primary Menu' ); I get a working menu.

<nav class="page-name">
    <div class="menu">
        <ul>
            <option id="menu-item-54" class="menu-item-54"><a></a></option>
            <option id="menu-item-24" class="menu-item-24"><a></a></option>
            <option id="menu-item-30" class="menu-item-30"><a></a></option>
            <option id="menu-item-18" class="menu-item-18"><a></a></option>
            <option id="menu-item-22" class="menu-item-22"><a></a></option>
            <option id="menu-item-26" class="menu-item-26"><a></a></option>
            <option id="menu-item-13" class="menu-item-13"><a></a></option>
            <option id="menu-item-28" class="menu-item-28"><a></a></option>
            <option id="menu-item-15" class="menu-item-15"><a></a></option>
            <option id="menu-item-2" class="menu-item-2"><a></a></option>
            <option id="menu-item-20" class="menu-item-20"><a></a></option>
        </ul>
    </div>
</nav>

This is what I get when using the exact same function in twenteleven theme (which is what I want):

<nav class="page-name">
    <div class="menu-nav-menu-container">
        <select>
            <option id="menu-item-59" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-59">Sample Page </option>
            <option id="menu-item-60" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-60">&nbsp;&nbsp;News</option>
            <option id="menu-item-65" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-65">About   </option>
            <option id="menu-item-62" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-62">&nbsp;&nbsp;Contact Us</option>
            <option id="menu-item-63" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-63">&nbsp;&nbsp;Our Location</option>
            <option id="menu-item-61" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-61">History</option>
            <option id="menu-item-64" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-64">Links</option>
        </select>
    </div>
</nav>

Update

I solved the problem. apparently the custom menu was selected when I used another theme and I assumed every theme will uset. well - no! I had to select custom menu for each theme separately.

Answer 1

Maybe you are doing it wrong? Here's a pointer...

In functions.php

// This theme uses wp_nav_menu() in one location.
register_nav_menus( array(
    'primary' => 'Primary Menu',
) );

In header.php (or elsewhere)

<?php wp_nav_menu( array( 'theme_location' => 'primary' ) ); ?>