follower

if ($xml[0]['gps-point'][$i]['lat'] - $x <= $xml[0]['gps-point'][$i - 1]['lat'] &&  $xml[0]['gps-point'][$i]['lat'] + $x >= $xml[0]['gps-point'][$i - 1]['lat'] || $xml[0]['gps-point'][$i]['lon'] - $x <= $xml[0]['gps-point'][$i - 1]['lon'] &&  $xml[0]['gp-point'][$i]['lon'] + $x >= $xml[0]['gps-point'][$i - 1]['lon'])