首先使用此代码填充父下拉列表。

<select id="parent">
    <option>-</option>
    <?php
        if(taxonomy_exists(\'parent_taxonomy_name\')):
            $results = get_terms(\'parent_taxonomy_name\',array(\'fields\'=>\'all\',\'parent\'=>0));
            if ($results):
                foreach ($results as $result):
    ?>                                                                 
                    <option value="<?php echo $result->name; ?>"><?php echo $result->name; ?></option>
    <?php 
                endforeach;
            endif;
        endif;
    ?>
</select>

 <select id="child">
        <option>-</option>
    </select>

jQuery("#parent").change(function(){
    jQuery.post(
        // see tip #1 for how we declare global javascript variables
        MyAjax.ajaxurl,
        {
            // here we declare the parameters to send along with the request
            // this means the following action hooks will be fired:
            // wp_ajax_nopriv_myajax-submit and wp_ajax_myajax-submit
            action : \'myajax-submit\',

            // other parameters can be added along with "action"
            parent : jQuery(this).val()
        },
        function( response ) {
            if(response[\'success\'] != false)
            {
                jQuery(\'#child\').empty().append(\'<option value="">Select Location</option>\');
                jQuery.each(response,function(index,value){
                    jQuery(\'#child\').append(\'<option value="\'+value+\'">\'+value+\'</option>\');
                });
            }
        }
    );
});

// if both logged in and not logged in users can send this AJAX request,
// add both of these actions, otherwise add only the appropriate one
add_action( \'wp_ajax_nopriv_myajax-submit\', \'myajax_submit\' );
add_action( \'wp_ajax_myajax-submit\', \'myajax_submit\' );

function myajax_submit() {
    // get the submitted parameters
    $parent = $_POST[\'parent\'];
    // generate the response
                $locations = ashyana_getTaxonomyValues( \'parent_taxonomy_name\', $parent, 0 );
                $results = array();
                if ($locations):
                    foreach ($locations as $location):                                
                        $loc[] = $location->name;
                    endforeach;
                    $response = json_encode( $loc );
                else:
                    $response = json_encode( array( \'success\' => false ) );
                endif;

    // response output
    header( "Content-Type: application/json" );
    echo $response;

    // IMPORTANT: don\'t forget to "exit"
    exit;
}