Reply To: Problem with acf relational field used as filter

Good evening,
I want to share my solution, thank you for your suggestions.
In configuration of plugin, I removed only “{get_values}”, but I leaved correct custom field name.
Than, simply I did populate options thanks to correct hook. In this way I dont need to manipulate results, because they remain alredy correct:

add_filter('asp_pre_get_front_filters', 'asp_change_a_filter', 10, 2);
function asp_change_a_filter($filters, $type) {
  foreach ($filters as $k => &$filter) {
		
    if ( $filter->type() == 'custom_field' && $filter->field() == 'recensore_aurotore_oblio' ) {

			$args = array(  
				'post_type' => 'recensorieautori',
				'post_status' => 'publish',
				'posts_per_page' => 999, 
				'orderby' => 'title', 
				'order' => 'ASC', 
		);
		$loop = new WP_Query( $args );

			while ( $loop->have_posts() ) : $loop->the_post();
				$filter->add(array(
        'label' =>  get_the_title(),
        'selected' => false,
        'value' => 'a:1:{i:0;s:3:"'. get_the_id() .'";}'
      ));
			endwhile;
   		wp_reset_postdata();       
    }   

	if ( $filter->type() == 'custom_field' && $filter->field() == 'numero_rivista' ) {

		$args = array(  
			'post_type' => 'numeridellarivista',
			'post_status' => 'publish',
			'posts_per_page' => 999, 
			'orderby' => 'title', 
			'order' => 'ASC', 
	);
	$loop = new WP_Query( $args );

		while ( $loop->have_posts() ) : $loop->the_post();
			$filter->add(array(
			'label' =>  get_the_title(),
			'selected' => false,
			'value' => 'a:1:{i:0;s:2:"'. get_the_id() .'";}'
		));
		endwhile;
		 wp_reset_postdata();       
	}   
}

  return $filters;
}