$url = "https://webhook.site/c2b3c020-baa3-4ae2-aba8-5df6a3ac01bd";
    $data = array("customfield" => $vars['customFields']);
    $options = array(
        'http' => array(
            'header'  => "Content-type: application/json\r\n",
            'method'  => 'POST',
            'content' => http_build_query($data)
        )
    );
    $context  = stream_context_create($options);
    $result = file_get_contents($url, false, $context);
    if ($result === FALSE) { echo "error"; }

    var_dump($result);