CAPTCHA

General PHP
1

I want to use a CAPTCHA for a form without Yii2 framework.Is there any suggestion for a simple CAPTCHA?

2

the default captcha is so simple. its for security man.

3

I do not use yii2 at this form/project,it is plain php/html.

I found this http://www.web1marketing.com/resources/tools/quickcaptcha/

Are there other good captcha scripts?