getDistanceFromLatLonInKm.php

<?php

function getDistanceFromLatLonInKm() {
    // $lat1,$lon1,$lat2,$lon2
    $lat1 = 23.747047;
    $lon1 = 90.386709;

    $lat2 = 23.783014;
    $lon2 = 90.395310;

    $R = 6371; // Radius of the earth in km
    $dLat = $this->deg2rad($lat2 - $lat1);  // deg2rad below
    $dLon = $this->deg2rad($lon2 - $lon1);
    $a =
      sin($dLat/2) * sin($dLat/2) +
      cos($this->deg2rad($lat1)) * cos($this->deg2rad($lat2)) *
      sin($dLon/2) * sin($dLon/2)
      ;
    $c = 2 * atan2(sqrt($a), sqrt(1-$a));
    $d = $R * $c; // Distance in km

    return $d;
}

function deg2rad($deg) {
    return $deg * (pi()/180);
}