//= First let’s modify the sorting form
add_filter(‘cd_sort_filter’, ‘my_car_demon_sort’,10,1);
function my_car_demon_sort($car_demon_sorting) {
 // $car_demon_sorting contains the current sorting content
 //= Put everything on a single line
 $car_demon_sorting = str_replace(chr(10),”,$car_demon_sorting);
 $car_demon_sorting = str_replace(chr(11),”,$car_demon_sorting);
 $car_demon_sorting = str_replace(chr(13),”,$car_demon_sorting);
 //= Search for the sorting drop down
 $start = ‘ tag and replace it with $new_option + 
 $drop_down_field = str_replace(‘‘, $new_option.’‘, $drop_down_field);
 //= Now search $car_demon_sorting for the original drop down and replace it with our new one
 $car_demon_sorting = str_replace($form_piece[0], $drop_down_field, $car_demon_sorting);
 }
 //= Return the modified sorting form
 return $car_demon_sorting;
}
//= Now we need to modify the query
add_filter(‘cd_query_filter’, ‘my_car_query’,10,1);
function my_car_query($car_demon_query) {
 // $car_demon_query contains the current query
 //= Check to make sure order_by was set
 if (isset($_GET[‘order_by’])) {
 //= Sanitize it and set it to a variable
 $order_by = sanitize_text_field($_GET[‘order_by’]);
 //= Since _stock_value is an existing meta field we can set it like this
 $car_demon_query[‘meta_key’] = $order_by;
 }
 return $car_demon_query;
}