TYPO3: Check which checkbox items got checked by bitwise shifting

FindActiveCheckboxesViewHelper.php

<?php
namespace HenrikZiegenhain\MyExt\ViewHelpers;

/***************************************************************
 *  Copyright notice
 *
 *  (c) 2018 Henrik Ziegenhain <[email protected]>
 *
 *  All rights reserved
 *
 *  This script is part of the TYPO3 project. The TYPO3 project is
 *  free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  The GNU General Public License can be found at
 *  http://www.gnu.org/copyleft/gpl.html.
 *
 *  This script is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  This copyright notice MUST APPEAR in all copies of the script!
 ***************************************************************/

use TYPO3\CMS\Fluid\Core\ViewHelper\AbstractViewHelper;

/**
 * Check which checkbox items got checked by bitwise shifting
 * Remember: TYPO3 saves da decimal representation of checkbox values to database
 * Example: "5" means, that Checkboxes No. 1 and 3 got checked (1 + 4)
 */
class FindActiveCheckboxesViewHelper extends AbstractViewHelper
{
    /**
     * Initialize arguments.
     */
    public function initializeArguments()
    {
        parent::initializeArguments();
        $this->registerArgument('value', 'int', 'decimal value of active checkboxes', true);
    }

    /**
     * @return array
     */
    public function render()
    {
        $checkboxValue = (int)$this->arguments['value'];
        $activeCheckboxes = [];
        for ($i=0; $i<10; $i++) {
            if (($checkboxValue >> $i) & 1) {
                /*
                 * Decide what kind of value you need, bit shift, item number or pow
                echo 'bit shift ' . $i . '<br>';
                echo 'pow ' . pow(2, $i) . '<br>';
                echo 'item #' . ($i+1) . '<br>';
                */
                $activeCheckboxes[] = $i+1;
            }
        }
        return $activeCheckboxes;
    }
}