how to limit the amount of comments or replies to comments a user can post per day

I have a comment section and a reply to comment section on my social network. We are having some trouble with manual spammers, and I was going to limit the amount of comments someone could post a day.

Here are the insert queries for comments and reply to comments:

//COMMENTS

$query = "INSERT INTO `CysticAirwaves` ( 
                                        `FromUserID`,
                                        `ToUserID`,
                                        `comment`,
                                        `status`,
                                        `statusCommentAirwave`,
                                        `date`,
                                        `time`

                                ) VALUES (

                                    '" . $auth->id ."',
                                    '" . $prof->id ."',
                                    '" . mysql_real_escape_string($_POST['ProfileComment']) ."',
                                    'active',
                                    'active',
                                    '" . date("Y-m-d") . "',
                                    '" . date("G:i:s") . "')";
    mysql_query($query,$connection); 

    if($auth->id == $prof->id) {
        $just_inserted = mysql_insert_id();
        $query = "UPDATE `CysticAirwaves` SET `status` = 'dead' WHERE `FromUserID` = '" . $auth->id . "' AND `ToUserID` = '" . $prof->id . "' AND `id` != '" . $just_inserted . "'";
        $request = mysql_query($query,$connection);
}

//REPLIES

$query = "INSERT INTO `CysticAirwaves_replies` (
                                    `AirwaveID`,
                                    `FromUserID`,
                                    `comment`,
                                    `status`,
                                    `date`,
                                    `time`
                                ) VALUES (
                                    '" . mysql_real_escape_string($_POST['comment']) . "',
                                    '" . $auth->id . "',
                                    '" . mysql_real_escape_string($_POST['reply']) . "',
                                    'active',
                                    '" . date("Y-m-d") . "',
                                    '" . date("G:i:s") . "'
                                    )";
    mysql_query($query,$connection);

    $mailto = array();

    /* get the person that wrote the inital comment */
    $query = "SELECT `FromUserID` FROM `CysticAirwaves` WHERE `id` = '" . mysql_real_escape_string($_POST['comment']) . "' LIMIT 1";
    $request = mysql_query($query,$connection);
    $result = mysql_fetch_array($request);
    $comment_author = new User($result['FromUserID']);

thanks in advance

Solution

You can perform a select to see how many entries are in the table already by that user for the current date:

SELECT COUNT(*)
FROM   CysticAirwaves
WHERE  userid = $auth->id
  AND  date = CURDATE()

Then only perform the INSERT if the number is below your threshold. Alternatively, you can place a trigger on the INSERT that does this check with every INSERT and bounces the call as well. ("Best practice" would be to place it in the database as this would be a database-related limitation, but that's your call)

It's been a while since I've done MySQL triggers, but I think think is what you're after:

delimeter |

CREATE TRIGGER reply_threshold BEFORE INSERT ON CysticAirwaves_replies
  FOR EACH ROW BEGIN
    DECLARE reply_count INT;
    SET reply_count = (SELECT COUNT(*) FROM CysticAirwaves_replies WHERE userid = NEW.userid AND `date` = CURDATE());
    IF reply_count > 5 THEN
      SIGNAL SQLSTATE SET MESSAGE_TEXT = 'Too many replies for today';
    END IF;
  END;

|
delimeter ;

Essentially, if you go to insert a reply in the table and the threshold has been exceeded, a sql error will be raised stopping the action. You can't "prevent" an insert per-say, but you can raise an exception that makes it fall-through.