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Killing comment spam in Textpattern

Although it’s nothing like on the scale that the most popular blogs see it, I’ve been having problems with comment spam – mostly of the texas-holdem, online casino and herbal viagra variety – so tonight I decided to do something about it.

Comments are parsed by the comment.php file under textpattern/publish, and the function that we are interested in is saveComment(), around line 277.

It already has some checks in there for empty name, email or comment fields, so it is easy to add a last check against a central list of blacklisted words – just add the following code after the comment_required check:


$spam = file("http://www.thewatchmakerproject.com/blacklist.txt");
for($i=0;$i < count($spam);$i++) {
if (stristr($message,trim($spam[$i]))) {
exit ( graf('You have used words that are in my spam blacklist - if your are making a legitimate comment, please go <a href="" onClick="history.go(-1)">'.gTxt('back').'</a> and try again.') );
}
}


Using the file function, we create a temporary array containing all the words in our spam blacklist, then iterate through it checking to see if any of the words are present in the comment submitted. As soon as one is found, we use the existing Textpattern graf() function to show a message to the commenter and stop processing the comment.

To add new blacklisted words, all we have to do is add a new line to the text file. Obviously if you use this on your own site, change the file reference to your own blacklist text file.

Filed under: Textpattern.

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