Save array data on WordPress Widgets

WP_Widget_update_array.php

<?php

/**
 * To be used on a WordPress Widget object
 * Fields named as '_foo_bar' will become $new_instance['foo']['bar'] = $val
 * Fields named as '_lorem_ipsum_dolor' become $new_instance['lorem']['ipsum']['dolor'] = $val
 **/

	function update( $new_instance, $old_instance ) {
		foreach ( $new_instance as $key => $val ) {
			if ( strpos($key, '_') === 0 && substr_count($key, '_') >= 2 ) {
				$new_key = explode('_', $key); $l = count($new_key);
				switch ( $l ) :
					case 3:
						$new_instance[$new_key[1]][$new_key[2]] = $val;
						break;
					case 4:
						$new_instance[$new_key[1]][$new_key[2]][$new_key[3]] = $val;
						break;
				endswitch;				
				unset($new_instance[$key]);
			}
		}
		return $new_instance;
	}
?>