calculate distance between two points in php

latlon.php

<?php

/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */
/*  based on :      https://github.com/chrisveness/geodesy                                        */
/*                                                                                                */
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */

/**
 * Class LatLon
 * Creates a LatLon point on the earth's surface at the specified latitude / longitude.
 */
class LatLon
{
    public $lat;
    public $lon;

    private $radius = 6371e3; // (Mean) radius of earth (defaults to radius in metres).

    function __construct($lat, $lon)
    {
        $this->lat = $lat;
        $this->lon = $lon;
    }


    /**
     * Returns the distance from 'this' point to destination point (using haversine formula).
     * @param {LatLon} $point - Latitude/longitude of destination point.
     * @return float Distance between this point and destination point, in same units as radius.(meters)
     */
    function distanceTo($point){
        if (!is_a($point, 'LatLon') || !is_a($point, 'LatLon'))
            return 0;

        //convert to radians
        $from = $this->toRadians();
        $to = $this->toRadians($point);

        $latDiff = $to->lat - $from->lat;
        $lonDiff = $to->lon - $from->lon;

        $a = sin($latDiff / 2) * sin($latDiff / 2) +
            cos($from->lat) * cos($to->lat) *
            sin($lonDiff / 2) * sin($lonDiff / 2);
        $c = 2 * atan2(sqrt($a), sqrt(1 - $a));
        return $d = $this->radius * $c;   // in meters
    }

    private function toRadians($point = null){
        $point = $point ? $point : $this;
        $point->lat *=  M_PI / 180;
        $point->lon *=  M_PI / 180;
        return $point;
    }

    public static function metersToMiles($i) {
        return $i*0.000621371192;
    }
    public static function milesToMeters($i) {
        return $i*1609.344;
    }
}

$from = new LatLon(48.857, 2.351);
echo LatLon::metersToMiles($from->distanceTo(new LatLon(52.205, 0.119)));