Calculate distance between 2 Coordinates

	public function DistAB($lata, $lona, $latb, $lonb)
	{
          $delta_lat = $latb - $lata ;
          $delta_lon = $lonb - $lona ;

          $earth_radius = 6372.795477598;

          $alpha    = $delta_lat/2;
          $beta     = $delta_lon/2;
          $a        = sin(deg2rad($alpha)) * sin(deg2rad($alpha)) + cos(deg2rad($lata)) * cos(deg2rad($latb)) * sin(deg2rad($beta)) * sin(deg2rad($beta)) ;
          $c        = asin(min(1, sqrt($a)));
          $distance = 2*$earth_radius * $c;
          $distance = round($distance, 4);

          return $distance;
	}