1. Go to this page and download the library: Download mdmsoft/yii2-captcha 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/ */
mdmsoft / yii2-captcha example snippets
public function actions()
{
return [
...
'captcha' => [
'class' => 'mdm\captcha\CaptchaAction',
'level' => 3, // avaliable level are 1,2,3 :D
],
];
}