PHP coords calculation

Coordinates.php

class Coordinates
{
    /**
     * @param array $c1 Expected [lat, lon] EPSG:4326
     * @param array $c2 Expected [lat, lon] EPSG:4326
     * @return float|int distance in meters
     */
    public function calculateDistance($c1, $c2)
    {
        $radius = 6371000;
        [$lat1, $lon1] = $c1;
        [$lat2, $lon2] = $c2;
        $dLon = deg2rad($lon2 - $lon1);
        $lat1 = deg2rad($lat1);
        $lat2 = deg2rad($lat2);
        return acos(
                sin($lat1) * sin($lat2) + cos($lat1) * cos($lat2) * cos($dLon)
            ) * $radius;
    }

    /**
     * @param array $coord Expected [lat, lon] EPSG:4326
     * @param float $bearing Bearing in degrees
     * @param float $distance Distance in meters
     * @return array [lat, lon] coordinate.
     */
    function createCoord($coord, $bearing, $distance)
    {
        $radius = 6371000;
        $δ = $distance / $radius;// angular distance in radians
        $θ = deg2rad($bearing);
        $φ1 = deg2rad($coord[0]);
        $λ1 = deg2rad($coord[1]);

        $φ2 = asin(sin($φ1) * cos($δ) +
            cos($φ1) * sin($δ) * cos($θ));

        $λ2 = $λ1 + atan2(sin($θ) * sin($δ) * cos($φ1),
                cos($δ) - sin($φ1) * sin($φ2));
        // normalise to -180..+180°
        $λ2 = fmod(($λ2 + 3 * pi()), (2 * pi())) - pi();

        return [rad2deg($φ2), rad2deg($λ2)];
    }

    /**
     * @param array $start Expected [lat, lon] EPSG:4326
     * @param array $end Expected [lat, lon] EPSG:4326
     * @return int Bearing in degrees.
     */
    function getBearing($start, $end)
    {
        $startLat = deg2rad($start[0]);
        $startLong = deg2rad($start[1]);
        $endLat = deg2rad($end[0]);
        $endLong = deg2rad($end[1]);
        $dLong = $endLong - $startLong;
        $dPhi = log(tan($endLat / 2.0 + pi() / 4.0) /
            tan($startLat / 2.0 + pi() / 4.0));

        if (abs($dLong) > pi()) {
            $dLong = ($dLong > 0.0) ? -(2.0 * pi() - $dLong) : (2.0 * pi() + $dLong);
        }
        return (rad2deg(atan2($dLong, $dPhi)) + 360.0) % 360.0;
    }
}