[Crystallize]

Hi guys , i'm in need of some help , i'm trying to make some radiation zones but when I compile it gives me lots of errors here's the script

Code:

new LoseHP[MAX_PLAYERS];

forward NegativeDown(playerid);

public OnPlayerUpdate(playerid) // 
{
    if(IsPlayerInRangeOfPoint(playerid, Float:range, Float:x, Float:y, Float:z))
    {
        LoseHP[playerid] = SetTimerEx("NegativeDown",1000,1,"i",playerid);
    }
    return 1;
}

public NegativeDown(playerid)
{
    new Float:health;
    GetPlayerHealth(playerid, health);
    SetPlayerHealth(playerid, health - 1.5); //
    return 1;
}
public OnPlayerDisconnect(playerid, reason)
{
KillTimer(LoseHP[playerid]);
return 1;
}

Here are the errors

Code:

 : error 017: undefined symbol "MAX_PLAYERS"
) : error 009: invalid array size (negative, zero or out of bounds)
 : warning 235: public function lacks forward declaration (symbol "OnPlayerUpdate")
 : error 017: undefined symbol "IsPlayerInRangeOfPoint"
 : error 017: undefined symbol "SetTimerEx"
 : error 017: undefined symbol "GetPlayerHealth"
 : error 017: undefined symbol "SetPlayerHealth"
 : warning 235: public function lacks forward declaration (symbol "OnPlayerDisconnect")
 : error 017: undefined symbol "KillTimer"

Could anybody help me?