[TheToretto]

SendClientMessageEx is in general a function in which you can format & send the message in the same line, which means you don't have to format it in a string then send it... So I suggest you to change your code into this:

PHP код:

if(killerid != INVALID_PLAYER_ID)
     {
          new string[156],WeaponName[24],VictimName[MAX_PLAYER_NAME],KillerName[MAX_PLAYER_NAME];
          GetPlayerName(playerid, VictimName, sizeof (VictimName));
          GetPlayerName(killerid, KillerName, sizeof (KillerName));
          GetWeaponName(GetPlayerWeapon(killerid), WeaponName, sizeof (WeaponName));
          format(string, sizeof(string),"you were killed by %s with weapons %s",KillerName,WeaponName);
          SendClientMessageEx(COLOR_YELLOW,playerid,string);
          format(string, sizeof(string),"you killed %s with weapons %s",VictimName,WeaponName);
          SendClientMessageEx(COLOR_YELLOW,killerid,string);
    } 


PHP код:

if(killerid != INVALID_PLAYER_ID) 
    { 
        new WeaponName[24],VictimName[MAX_PLAYER_NAME],KillerName[MAX_PLAYER_NAME]; 
        GetPlayerName(playerid, VictimName, sizeof (VictimName)); 
        GetPlayerName(killerid, KillerName, sizeof (KillerName));
        GetWeaponName(GetPlayerWeapon(killerid), WeaponName, sizeof (WeaponName)); 
        SendClientMessageEx(playerid, COLOR_YELLOW, "you were killed by %s with weapons %s",KillerName,WeaponName);
        SendClientMessageEx(killerid, COLOR_YELLOW, "you killed %s with weapons %s",VictimName,WeaponName);
    } 


Plus you switched playerid with the color (Syntax: "SendClientMessage(playerid, color, const message[])" ) and it's the same for SendClientMessageEx