How can I add captcha in my contact form in PHP?

By distinguishing between humans and automated computer programs, CAPTCHA offers safety and security in a number of ways. Why use CAPTCHA:

1) Protecting Registration Forms in Websites

2) Preventing Spam Comments

3) Making Online Shopping More Secure

4) Protecting Email Accounts

It is very easy to implement a Captcha in any html forms using php. you can go through any of below mention links to implement it.

A Simple PHP CAPTCHA Script

How to Create CAPTCHA Protection using PHP and AJAX

Simple captcha code in php

Happy coding.