PHP stream context POST redirect problem

gistfile1.php

<?php

$base64cred = '<your auth data here>'; // base64_encode('username:password');

/** @var string Contains the redirect url */
$redirectUrl = null;

/**
 * Used to catch the redirect location
 */
function stream_notification_callback($notification_code, $severity, $message, $message_code, $bytes_transferred, $bytes_max)
{
    global $redirectUrl;
    switch ($notification_code) {
        case STREAM_NOTIFY_REDIRECTED:
            $redirectUrl = $message;
            break;
    }
}

// Create, will fail with a 401 error
$options = array(
    'http' => array(
        'method' => 'POST',
        'follow_location' => false,
        'header' => array(
            'Content-Type: application/json',
            'Authorization: Basic ' . $base64cred,
        ),
        'content' => '{"scopes":["repo"],"note":"Composer Debug","note_url":"https:\/\/getcomposer.org\/"}'
    ),
);
$ctx = stream_context_create($options, array("notification" => "stream_notification_callback"));
$result = file_get_contents('https://api.github.com/authorizations', null, $ctx);

// GET the created auth will work
$getOptions = array(
    'http' => array(
        'method' => 'GET',
        'header' => array(
            'Content-Type: application/json',
            'Authorization: Basic ' . $base64cred,
        ),
    ),
);
$ctx = stream_context_create($getOptions);
$result = file_get_contents($redirectUrl, null, $ctx);

var_dump($result);