[suhrab_mujeeb]

pawn Code:

// Top of the script
new PlayerWorld;

// Under OnGameModeInit
PlayerWorld = 0;

// Under OnPlayerConnect
PlayerWorld++;

// Under OnPlayerDisconnect
PlayerWorld--;

// Under OnPlayerSpawn
SetPlayerVirtualWorld(playerid, PlayerWorld);

Try this, untested.
Basically the same as MP2 said, I was making it while he posted it.