So you want to count posts that have a field named ‘aangeboden_door’ with several different values? I think you’ll have to modify the function so as to add meta_value as an array (of values) and setting ‘compare’ => ‘IN’. Try something like this:
// ...
if ( $meta_key && $meta_value ) {
if ( is_array($meta_value) ) {
$args['meta_query'][] = array('key' => $meta_key, 'value' => $meta_value, 'compare' => 'IN');
}
else {
$args['meta_query'][] = array('key' => $meta_key, 'value' => $meta_value);
}
}
// ...
