How to Insert Captcha Code into PHP Web Form

CAPTCHA: Telling Humans and Computers Apart Automatically (Stop Spam, Read Books)

Web form with Captcha code

Error message for invalid Captcha code

Insert Captcha PHP code in <Form> PHP page before Submit button

Insert Captcha PHP code on <Form> post action PHP page

URL: http://www.captcha.net/

Review:

A CAPTCHA is a program that protects websites against bots by generating and grading tests that humans can pass but current computer programs cannot. For example, humans can read distorted text as the one shown below, but current computer programs can't. The term CAPTCHA (for Completely Automated Public Turing Test To Tell Computers and Humans Apart) was coined in 2000 by Luis von Ahn, Manuel Blum, Nicholas Hopper and John Langford of Carnegie Mellon University.

Assumption:

Using reCAPTCHA with PHP.

Web form page and form post action page must be saved in *.php file.

Web server must support PHP.

Instruction:

1. Sign up for an API key at https://developers.google.com/recaptcha/

2. You'll need a Google (Gmail) account for this.

3. Enter your web site domain(s) that you want to use Captcha code.

4. Copy the public key and private key out.

5. Grab the PHP codes from https://developers.google.com/recaptcha/docs/php

6. There are 2 sets of PHP codes for PHP form page and PHP form post action page.

7. Embed the PHP codes into both PHP pages, don't forget to input your public key and private key accordingly.

8. Download the reCAPTCHA PHP library from https://code.google.com/p/recaptcha/downloads/list?q=label:phplib-Latest

9. Unzip the file.

10. Upload "recaptchalib.php" file onto web server, the same directory as your two PHP form pages are.

11. Captcha code installation on web form completed.

Note:

Always have a backup copy of your PHP form pages. Just so if you screw up the PHP page(s), you have a previous good working copy to roll back.