PHP function to get markers within certain radius

getCoordinatesWithinRadius.php

<?php

/**
 * @author Mohammad Mursaleen
 * @usange to get array of all markers within certain radius
 * @param $coordinateArray
 * @param $center
 * @param $radius
 * @return array
 */
function mm_getCoordinatesWithinRadius ( $lat1 , $lng1 , $radius , $available_markers ) {

    $stores_data = $available_markers;
    $resultArray= array();

    foreach ( $stores_data as $store ) {

        $lat2 = $store->lat;
        $lng2 = $store->lng;
        $distance = 3959 * acos(cos(mm_radians($lat1)) * cos(mm_radians($lat2)) * cos(mm_radians($lng2) - mm_radians($lng1)) + sin(mm_radians($lat1)) * sin(mm_radians($lat2)));
        if ($distance < $radius){

            $resultArray[] = (object) array( 'ID' => $store->ID , 'lat' => $store->lat , 'lng' => $store->lng , 'distance' => $distance );

        }

    }

    // need to return id,distance,lat and lng
    return $resultArray;

}

/**
 * @usage to convert degree into radians
 * @param $deg
 * @return float
 */
function mm_radians($deg) {

    return $deg * M_PI / 180;

}