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No more spam; Akismet and PHP to the rescue!

(Page 1 out of 2)


In this article you'll learn how to use the Akismet anti-spam service to prevent any spam from being added to your PHP website. Live examples and demo's are included.


Spam is one of the biggest problems on the internet, and I'm sure you've received a fair share of spam in your inbox as well. It's always been a cat-and-mouse game between developers and spammers, and it seems the spammers are always one step ahead. Simple measures like black lists or URL filtering simply don't work anymore, and spam always finds its way through. That's why we need a different solution, one that actually works. Introducing Akismet, the anti-spam service by the brilliant guys from Automattic who are also behind WordPress and

I've started using Akismet myself recently, and it has completely cut down all the spam I was receiving. Normally I'd get about 700 spam comments a day on my various blogs and websites (including PHPit), but since installing Akismet I've only received four. That means that approximately 99,5% is being caught by Akismet, which is an extremely good rate, and what's even better is that Akismet hasn't caught one good spam comment (no positives). Sounds pretty good, right?

That's why in this article I'll show you how to integrate Akismet in your own PHP scripts. But first let's have a closer look at how Akismet works.

How Akismet works

Akismet is basically a web service which analyzes your comments. Your script sends the contents of the comment to the Akismet service, using standard HTTP commands, and then Akismet analyzes the comment, and returns a thumbs up or down on the comment. Since Akismet is used by some many people (34,216,155 spams caught so far) its ability to analyze a comment is excellent, and it can detect almost any type of spam, and it's also smart enough to let normal comments go through.

Of course, nothing is perfect, so Akismet is bound to make a few mistakes here and there. That's why it's also possible to send suggestions to the Akismet service. If you discover that Akismet has missed a spam message, you can tell Akismet it's spam after all, which improves the analyzing ability of Akismet. Similarly, it's also possible to tell Akismet a message is actually a "good" comment and not spam after all.

A common problem with these types of central anti-spam services is that it's very easy for spammers to poison the spam database, by marking spam comments as good comments and good comments as spam. According to the Akismet FAQ, they have developed an algorithm against this type of behavior, but you also need an API key to use Akismet, so it's very easy for the people behind Akismet to ban any user.
Let's get started with some code, so quickly get your API key at, since you need to have an API key to use Akismet. When you have your API key, continue with this article.

Using the Akismet service

Akismet is very easy to use, and it's all basic REST calls, and all you really need to use is the fsockopen() function to send requests to Akismet. The full API documentation can be found by clicking here.

But since we're a lazy bunch we're going to use a pre-made PHP class which handles all the nitty gritty for us, leaving only the easy things. Head on over to the Akismet Development Page and download the PHP 4 class by Bret Kuhns.

Let's get started with an example, which demonstrates the basic usage of the Akismet service, using the PHP class by Bret:

include ('Akismet.class.php');

// Create object instance, and pass website URL and API key
$akismet = new Akismet('', '[YOUR API KEY HERE]');

$comment = "Hi!\n\nI really like your website\n\n\"\">Buy Viagra";

$akismet->setCommentAuthor('Buy my viagra');
$akismet->setCommentAuthorEmail('[email protected]');

if($akismet->isCommentSpam() == true) {
        echo 'We don\'t want your spam, punk!';
} else {
        echo 'Great comment, thanks!';


As you can see, it's really simple to use Akismet. Let's go through this example. First, we create a new instance of the Akismet class, and immediately pass the URL of our website and our API key. These two values are required by Akismet, and especially the API key must be correct. If this is incorrect, you will get a fatal error and the script execution will be halted, so make sure it's correct.

In the next few lines we set various properties of the comment which have been submitted by someone. In the example we use fixed values, which are very spammy (buy Viagra, casino's, etc).

Finally, we use the isCommentSpam() method to check whether the comment is spam. I'm sure you can guess the outcome in this example. And that's all really; I told you it was easy!

If you want to play with Akismet yourself and test different messages, click here for a live demo.

Next: Helping Akismet & Conclusion »

3 Responses to “No more spam; Akismet and PHP to the rescue!”

  1. Richard@Home » Blog Archive » links for 2006-05-23 Says:

    […] PHPit - Totally PHP » No more spam; Akismet and PHP to the rescue! How to plug the Akismet spam filter into your own PHP website (tags: php spam akismet) […]

  2. Matthijs Says:

    Hi Dennis,

    great article. Just installed Akismet (via the wp plugin) and it stopped all spam so far. Untill now I had to see that spam got through, and each time I had to copy-paste those nasty spam words to my growing list of bad words.

    I will use your article to use this for a guestbook script I wrote.

    However, is there any way to get me/us the class from Bret you link to (since the link doesn’t work anymore)?
    (you know how to contact me)

  3. Bret Kuhns Says:

    Sorry about the dead link. The one linked from the Akismet site is now active again!

Leave a Reply

About the author
Dennis Pallett is the main contributor to PHPit. He owns several websites, including ASPit and Chill2Music. He is currently still studying.
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