[Mugala]

you have no any reset for this, u're just increasing and increasing, that's a reason why u're getting this.

try this:
at the top of code

PHP Code:

SpamMessages[MAX_PLAYERS],SpamChecker[MAX_PLAYERS]; 


put this code at OnPlayerConnect (or if u have a login system, place at login)

PHP Code:

SpamChecker[playerid] = SetTimerEx("CheckSpam",1000,1,"i",playerid); // u can increase this timer. 


now, put this code at OnPlayerText

PHP Code:

if(PlayerData[playerid][MutedTime] <= 0) SpamMessages[playerid] ++;
if(SpamMessages[playerid] >= 5)
{
    PlayerData[playerid][Muted] = 1;
    PlayerData[playerid][MutedTime] += 20;
    new str[128]; // blah blah
    mysql_format(SQL, str,128,"UPDATE `users` SET `Muted`='1' ,`MutedTime`='%d' WHERE `id` = '%d' LIMIT 1",PlayerData[playerid][MutedTime],PlayerData[playerid][ID]); 
    mysql_tquery(SQL, str, "", ""); 
    SendClientMessage(playerid, COLOR_GREY, "You have been auto-muted for spamming. You will be unmuted in 20 seconds."); 
    return 0; 
} 


and now, build the reset function.

PHP Code:

forward CheckSpam(playerid);
public CheckSpam(playerid)
{
    if(SpamMessages[playerid] >= 5 && PlayerData[playerid][MutedTime] <= 0)
    {
        PlayerData[playerid][Muted] = 1;
        PlayerData[playerid][MutedTime] += 20;
        new str[128]; // blah blah
        mysql_format(SQL, str,128,"UPDATE `users` SET `Muted`='1' ,`MutedTime`='%d' WHERE `id` = '%d' LIMIT 1",PlayerData[playerid][MutedTime],PlayerData[playerid][ID]); 
        mysql_tquery(SQL, str, "", ""); 
        SendClientMessage(playerid, COLOR_GREY, "You have been auto-muted for spamming. You will be unmuted in 20 seconds."); 
    }
    else SpamMessages[playerid] = 0;
    return 1;
} 


place this code at OnPlayerDisconnect

PHP Code:

KillTimer(SpamChecker[playerid]);