GetPlayerOldState

#define GetPlayerOldState(%0) GetPVarInt(%0, "PLAYER_OLD_STATE")

public OnPlayerStateChange(playerid, newstate, oldstate)
{
    SetPVarInt(playerid, "PLAYER_OLD_STATE", oldstate);
    return 1;
}

// example
public OnPlayerDeath(playerid, killerid, reason)
{
    if(GetPlayerOldState(playerid) == PLAYER_STATE_DRIVER) print("1");
    else print("0");
    return 1;
}