//function forwards
forward timer_vehDestruct();

//global variables
new vehDestructTimer[MAX_VEHICLES];

//functions
public timer_vehDestruct(){
   for(new i; i<MAX_VEHICLES; i++) //for every vehicle
      if(vehDestructTimer[i]>300) //with a timer >= 300 seconds
         SetVehicleToRespawn(i); //destroy the vehicle
      else if(vehDestructTimer[i]>0) //otherwise, with a timer variable => 1
         vehDestructTimer[i]++; // increment the time variable. 
}

//callbacks
public OnPlayerExitVehicle(playerid, vehicleid)
{
        if(vehDestructTimer[vehicleid] == 0)
                vehDestructTimer[vehicleid] = 1;

	return 1;
}