A walker class to use that extends wp_dropdown_categories and allows it to use the term's slug as a value rather than ID

sh-wp-dropdown-taxonomies.php

<?php

/* 
 * A walker class to use that extends wp_dropdown_categories and allows it to use the term's slug as a value rather than ID.
 *
 * See http://core.trac.wordpress.org/ticket/13258
 *
 * Usage, as normal:
 * wp_dropdown_categories($args);
 *
 * But specify the custom walker class, and (optionally) a 'id' or 'slug' for the 'value' parameter:
 * $args=array('walker'=> new SH_Walker_TaxonomyDropdown(), 'value'=>'slug', .... );
 * wp_dropdown_categories($args);
 * 
 * If the 'value' parameter is not set it will use term ID for categories, and the term's slug for other taxonomies in the value attribute of the term's <option>.
*/

class SH_Walker_TaxonomyDropdown extends Walker_CategoryDropdown{

    function start_el(&$output, $category, $depth, $args) {
        $pad = str_repeat('&nbsp;', $depth * 3);
        $cat_name = apply_filters('list_cats', $category->name, $category);

        if( !isset($args['value']) ){
            $args['value'] = ( $category->taxonomy != 'category' ? 'slug' : 'id' );
        }

        $value = ($args['value']=='slug' ? $category->slug : $category->term_id );

        $output .= "\t<option class=\"level-$depth\" value=\"".$value."\"";
        if ( $value === (string) $args['selected'] ){ 
            $output .= ' selected="selected"';
        }
        $output .= '>';
        $output .= $pad.$cat_name;
        if ( $args['show_count'] )
            $output .= '&nbsp;&nbsp;('. $category->count .')';

        $output .= "</option>\n";
        }

}

Cleaned up some syntax errors, as pointed out here: http://wordpress.stackexchange.com/questions/57823/why-id-in-urls-doesnt-work-and-slug-yes/57843#comment75139_57843

Wonderful. (: This helped me out a lot, thank you.

Thank you, Stephen. You save my time so much!

Thank you, Stephen! Helped me a lot with my current project.

Hello Stephen, apologies if this is not the right place to ask.. I was wondering how to better remove 'value="0"' on $show_option_all argument? I have a GET search form and if $show_option_all option is selected, then I'm getting select_name=0 in my URL and I don't want it appear at all if $show_option_all option is selected. Any advice what to do?

Many thanks!

Hi Stephen,
I had been using this for few projects. But for a new one, I get below error:

Strict Standards: Declaration of SH_Walker_TaxonomyDropdown::start_el() should be compatible with Walker_CategoryDropdown::start_el(&$output, $category, $depth = 0, $args = Array, $id = 0) in

hchouhan: if you modify the function call to be start_el( &$output, $category, $depth = 0, $args = array(), $id = 0 ) { That will fix it. SH_Walker_TaxonomyDropdown has different arguments from what Walker_CategoryDropdown has defined, this will make them as the same. Note the defaults on '''$depth''', and '''$id'''

Thanks for this. Saved me a bunch of time and effort digging around and looking for the original walker and modifying it.

This is going to be included in one of my public plugins. "Media Categories".
https://github.com/eddiemoya/Media-Categories

thank for sharing!

Wonderful, saved my time. Than you for sharing the code.