Crea filtro di ricerca per un campo ACF object #acf #filter #backend

functions.php

//Crea filtro dropdown backend per un campo ACF di tipo object
/** Create the filter dropdown */
add_action( 'restrict_manage_posts', 'wpse45436_admin_posts_filter_restrict_manage_posts' );
 <?php 
function wpse45436_admin_posts_filter_restrict_manage_posts(){
    global $post;
    $type = 'materiale';
    if (isset($_GET['post_type'])) {
        $type = $_GET['post_type'];
    }
 
    //add filter to the post type you want
    if ('materiale' == $type){ //Replace NAME_OF_YOUR_POST with the name of custom post
        $values = array();

        //genero array [label] = valore per i campi option
        $args = array(
            'post_type' => 'product',
            'posts_per_page' => 500,
            );
    
        $loop = new WP_Query( $args );
        if ( $loop->have_posts() ) {
            while ( $loop->have_posts() ) : $loop->the_post();
                $values[get_the_title()] = get_the_ID();
            endwhile;
        } 
        
        wp_reset_postdata();

        ?>
        <select name="ADMIN_FILTER_FIELD_VALUE">
<option value=""><?php _e('Filtra per corso', '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 } } /** if submitted filter by post meta */ 
        add_filter( 'parse_query', 'wpse45436_posts_filter' ); 
        function wpse45436_posts_filter( $query ){ 
            global $pagenow; 
            $type = 'materiale'; 
            if (isset($_GET['post_type'])) { 
                $type = $_GET['post_type']; 
            } 
            //Replace NAME_OF_YOUR_POST with the name of custom post 
            if ( 'materiale' == $type && is_admin() && $pagenow=='edit.php' && isset($_GET['ADMIN_FILTER_FIELD_VALUE']) && $_GET['ADMIN_FILTER_FIELD_VALUE'] != '') { 
                $query->query_vars['meta_key'] = 'corso'; //Replace META_KEY to the actual meta key
            $query->query_vars['meta_value'] = $_GET['ADMIN_FILTER_FIELD_VALUE'];
            $query->query_vars['meta_compare'] = 'IN'; //necessario per la query di tipo object
            }
}