Prevent user from Sending Duplicate messages using PHP [closed]

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can anyone suggest a good PHP function, script, or method to Prevent user from Sending Duplicate messages?

Here's the scenario. I own a community website. Members can send each other messages. Then some spammers from Africa contacted all members by sending copy paste messages. How can I prevent this?

I've seen some website implements similar functionality. When a user send 3 messages and the website detected that those 3 messages are duplicates/similar. It warns the user against spamming.

Does anyone know of a function or script in PHP that I could use? Thank you in advance.

Answer 1

The first thing to do is to define the rule. For example, if you consider that you send three messages exactly, can be very easy to bypass the system.

One suggestion I had used for something like this - is this function http://php.net/similar_text

$var_1 = 'PHP IS GREAT';
$var_2 = 'WITH MYSQL';

similar_text($var_1, $var_2, $percent);

echo $percent;
// 27.272727272727

similar_text($var_2, $var_1, $percent);

echo $percent;
// 18.181818181818 

Then check the user history, if the last 3 messages had 80% or more similar you block the user.