Hierarchical select for native Advanced Custom Fields taxonomy fields.

custom-acf-admin.js

jQuery(document).ready(function($){

	//Modify select2 ajax request to include a parent_id parameter, used by custom_acf_taxonomy_hierarchy()
	acf.add_filter('select2_ajax_data', function( data, args, $input, field, instance ){

		var target_field_key = 'field_5c7634ca3413f'; //YOUR TARGET FIELD KEY HERE

		if(data.field_key == target_field_key){

			var parent_id = 0; //by default we want terms with parent of 0 (top level)
			
			if($input.val() != '' && $input.val() != null){ //if we have chosen one or more terms already
				var values = $input.val();
				parent_id = values.pop(); //get last selected term to use as the parent for the next query
			}
	
			data.parent = parent_id;
		}

	  return data;

	});
	
});

hierearchical-select-acf.php

<?php

//Modifies ajax requests from our select2 dropdown, $args = WP_Term_Query arguments
function custom_acf_taxonomy_hierarchy( $args, $field, $post_id ){
    //default to 0 (top-level terms only) unless we get a different parent with the request
    $args['parent'] = empty($_POST['parent']) ? 0 : $_POST['parent'];
    
    //To allow multiple top-level selections, we can go back to the top of the taxonomy tree after we reach the end of a branch
    /*
    if(!empty($args['parent'])){
        $child_terms = get_term_children($args['parent'],'YOUR_TAXONOMY_SLUG'); //change to your taxonomy slug
        if(empty($child_terms) || is_wp_error($child_terms)) $args['parent'] = 0;
    }
    */
    
    return $args;
}
add_filter('acf/fields/taxonomy/query/key=field_5c7634ca3413f', 'custom_acf_taxonomy_hierarchy',10,3);


//Make the javascript available in the admin when editing a post with ACF
function custom_admin_enqueue_scripts(){        
    wp_enqueue_script('custom-acf-admin-js', get_stylesheet_directory_uri() . '/js/custom-acf-admin.js',['jquery']);
}
add_action('acf/input/admin_enqueue_scripts','custom_admin_enqueue_scripts');

@MogulChris Thanks very much for your help!!!! You've saved my day :)

Hello everyone, I've been looking for this solution for the past two days, Great I've found it but am not good at PHP and jQuery.

Am using ACF Frontend to allow users to submit their products via a frontend form.

after reading some articles on how to use jQuery in WP, I create a js folder in my child theme directory and uploaded the jQuery file. (customized the field key and also I didn't change the naming of the js file.)

I added the PHP code to the functions.php of my child theme but there is no change.

I'd request you guys to help me out on how to make it work. Thank you

Is it possible not working anymore under ACF Version 6.0.5 and/or PHP 8.1? Has somebody an idea why?
Thanks a lot!

albertvisuals

FOund some workaround/fix?