Blog > April 2009

SPAM Protection Using PHP and jQuery

The most common solution to keep 'machines/automated spammers' from abusing PHP forms is to use a CAPTCHA. This works, for the most part, but is very inconvenient & usually unsightly for the visitor, discouraging them from actually using the form for its intended purpose.

The solution we've come up with is much simpler than other proposed solutions we've run across.  We hope you find it helpful.

Here's how it works: (view demo · source · download)

• Give your required form field a specific class
  
• After a visitor enters information in the text field, a call is made to the PHP script, using jQuery
  
• The PHP script sets a session, confirming that the visitor is actually a real person since they must have clicked on one of the form fields.
  
• Since the session is set, the visitor is allowed to send the form.

The only downside we can think of is that the form won't work unless the visitor has Javascript enabled, but typically over 95% of visitors to your site will have Javascript enabled.

 
UPDATE:  (4/10) - Looks like someone else had a similar idea first:  http://15daysofjquery.com/examples/contact-forms