Adding Akismet.com spam checks to your contact form

I had a request the other day to write a spam filter for a standard contact form. Thanks to wordpress I’ve been made aware of the excellent spam filtering service offered by Akismet.com. What’s even better, is that an Akismet Service class has been added to the Zend Framework – allowing for easy integration into one’s PHP projects.

The code posted below makes the following assumptions :

• You have an Akismet API key
• You have the Zend Framework installed and configured correctly : click here for documentation
• You have written the form HTML, the form has been submitted and all input data has been sanitized (make sure to read the comments).
  
• You know how to use the php mail() function or have an equivalent method

<?php
/*
* Basic function to check for spam
* @param items : associative array for containing form field values
* @return boolean : true if spam, false if clean
*/
function spamCheck($items){
 	require_once 'Zend/Service/Akismet.php'; // include the required class file - change path if necessary
 	$url = "http://url.to.my.blog.or.form"; // url associated with API key
	$api = "432dsjk890"; // Akismet API key
 	$spam = new Zend_Service_Akismet($api, $url ); // create new instance of our Akismet Service class

	if ($spam->verifyKey()){ // make sure the API key if valid before performing check
	 	$params = array(); // check the comments for the isSpam() method in Zend/Service/Askismet.php for more information on available parameters
	 	$params["user_ip"] = $_SERVER['REMOTE_ADDR']; // required by Akismet
	 	$params["user_agent"] = $_SERVER['HTTP_USER_AGENT']; // required by Akismet
	 	$params["referrer"] = $_SERVER[ 'HTTP_REFERER'];
	 	$params["comment_type"] = "comment";
	 	$params["comment_author"] = $items["name"];
	 	$params["comment_author_email"] = $items["email"];
	 	$params["comment_content"] = $items["comments"];

	 	return $spam->isSpam($params); // submits api call and returns true if spam, false if clean

	} else {
 		return false;
 	}
 }

// to make use of our spam check function try the following :
$items = sanitize($_POST); // sanitize is your own built-in function to sanitize user submitted data

// only mail the form contents if not spam
if (!spamCheck($items)){
	// insert code to mail form contents here
}
?>

This is of course a very basic example, and only touches on the isSpam() method provided by the class. The real power is actually contained in the submitSpam() and submitHam() methods on which I will be posting a tutorial shortly.