Woocommerce Custom Admin Filter Dropdown

woo-custom-admin-filter.php

<?php
//Add custom filter dropdown to admin for CPT
function wpse45436_admin_posts_filter_restrict_manage_posts(){
    $type = 'post';
    if (isset($_GET['post_type'])) {
        $type = $_GET['post_type'];
    }

    //only add filter to post type you want
    if ('product' == $type){
        //change this to the list of values you want to show
        //in 'label' => 'value' format
        $values = array(
            'Yes' => 'Yes', 
        );
        ?>
        <select name="ADMIN_FILTER_FIELD_VALUE">
        <option value=""><?php _e('Filter by Sold ', 'wose45436'); ?></option>
        <?php
            $current_v = isset($_GET['ADMIN_FILTER_FIELD_VALUE'])? $_GET['ADMIN_FILTER_FIELD_VALUE']:'';
            foreach ($values as $label => $value) {
                printf
                    (
                        '<option value="%s"%s>%s</option>',
                        $value,
                        $value == $current_v? ' selected="selected"':'',
                        $label
                    );
                }
        ?>
        </select>
        <?php
    }
}
add_action( 'restrict_manage_posts', 'wpse45436_admin_posts_filter_restrict_manage_posts', 50);

//Bring the results from the filter dropdown
function wpse45436_posts_filter( $query ){
    global $pagenow;
    $type = 'post';
    if (isset($_GET['post_type'])) {
        $type = $_GET['post_type'];
    }
    if ( 'product' == $type && is_admin() && $pagenow=='edit.php' && isset($_GET['ADMIN_FILTER_FIELD_VALUE']) && $_GET['ADMIN_FILTER_FIELD_VALUE'] != '') {
        $query->query_vars['meta_key'] = 'sold'; //change this for your custom field name
        $query->query_vars['meta_value'] = $_GET['ADMIN_FILTER_FIELD_VALUE'];
    }
}
add_filter( 'parse_query', 'wpse45436_posts_filter' );