1. Go to this page and download the library: Download dhtmlx/dhtmlx-gii library. Choose the download type require.
2. Extract the ZIP file and open the index.php.
3. Add this code to the index.php.
<?php
require_once('vendor/autoload.php');
/* Start to develop here. Best regards https://php-download.com/ */
dhtmlx / dhtmlx-gii example snippets
//if your gii modules configuration looks like below:
$config['bootstrap'][] = 'gii';
$config['modules']['gii'] = 'yii\gii\Module';
//remove this two lines