GetVehicleWithinDistance( playerid, Float:x1, Float:y1, Float:z1, Float:dist, &veh){//It should be in script other wise the GetVehicleWithInDistance will not work
    for(new i = 1; i < MAX_VEHICLES; i++){
        if(GetVehicleModel(i) > 0){
            if(GetPlayerVehicleID(playerid) != i ){
            new Float:x, Float:y, Float:z;
            new Float:x2, Float:y2, Float:z2;
            GetVehiclePos(i, x, y, z);
            x2 = x1 - x; y2 = y1 - y; z2 = z1 - z;
            new Float:vDist = (x2*x2+y2*y2+z2*z2);
            if( vDist < dist){
            veh = i;
            dist = vDist;
                }
            }
        }
    }
}

GetVehicleWithinDistance(playerid, x, y, z, 8.0, veh);