Get heading from two lat/lng points

TwoPointHeading.php

<?php

function computeHeading($from, $to) {
    $fromLat = deg2rad($from['lat']);
    $fromLng = deg2rad($from['lng']);
    $toLat = deg2rad($to['lat']);
    $toLng = deg2rad($to['lng']);
    $dLng = $toLng - $fromLng;

    $heading = rad2deg(
        atan2(
            sin($dLng) * cos($toLat),
            cos($fromLat) * sin($toLat) - sin($fromLat) * cos($toLat) * cos($dLng)
        )
    );

    $min = -180;
    $max = 180;

    if ($heading >= $min && $heading < $max) {
        return $heading;
    }

    $x = $heading - $min;
    $m = $max - $min;

    return ((($x % $m) + $m) % $m) + $min;
}

$from = ['lat' => 52.027254, 'lng' => 8.539802];
$to = ['lat' => 52.024667, 'lng' => 8.539887];

$heading = computeHeading($from, $to);

echo $heading;