How do I make a spam filter?

The title says it all.

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So basically, select from the table where the poster=logged in user and use if(mysql_num_rows($query)==1){die("You posted ".$_POST['status']."already!");}

Is that what you do?

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Alongside a duplicate checker, you may also want a user input limiter. Which would restrict by time. One of the more basic methods entails having a timer and locking/unlocking the queue based on the amount of time elapsed. Specific intervals would vary with use, e.g. chatroom, comments.

Catch my drift.

Hmm... i made on but different

A true developer

You could simply have PHP (or whatever server-side language you're using) check if the most recent posts (say, 2) are from the same user and disallow further posting from that user until another has posted.

It's my job to help the next generation, and set a good example for them. And for that I'll gladly lay down my life.

Id say 3 posts in 5 seconds. enouh time to type msgs, not enough to spam ;D

I'll be back every now and then

You can do this with javascript :o i need tto learn php >-<