RecursiveCategories.php

<?php
namespace App\Helpers;

abstract class RecursiveCategories
{
    public static function getChildren($items, $parent = 0)
    {
        $element = [];
        foreach ($items as $item) {
            if ($item['parent_id'] == $parent) {
                $element[$item['id']] = $item;
                $element[$item['id']]['children'] = self::getChildren($items, $item['id']);

            }
        }
        return $element;
    }
    
    /**
     * @param $items
     * @param null $selectedCats
     * @param string $inputName
     * @param string $disabledCats
     * @return string
     */
    public static function buildCategoryTree($items, $selectedCats=null, $inputName='categories', $disabledCats = null)
    {
        $tree = '<ul>';

        $selectedCategories = explode(',', $selectedCats);
        $disabledCategories = explode(',', $disabledCats);
        foreach($items as $item){

            if(in_array($item['id'], $disabledCategories)){
                $disabled = 'disabled="disabled"';
            }else{
                $disabled = '';
            }

            if(in_array($item['id'], $selectedCategories)){
                $selected = 'checked="checked"';
            }else{
                $selected = '';
            }

            $tree .= '<li><input '.$disabled.' '.$selected.' type="checkbox" value="'.$item['id'].'" name="'.$inputName.'[]"><span>'.$item['title'].'</span>';

            if(!empty($item['children'])){
                $tree .= self::buildCategoryTree($item['children'], $selectedCats, $inputName);
            }
            $tree .= '</li>';
        }


        $tree .='</ul>';
        return $tree;
    }
}