json_encode($arr, JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES);

function mail_utf8($to, $from_user, $from_email,
                   $subject = '(No subject)', $message = '')
{
    $from_user = "=?UTF-8?B?".base64_encode($from_user)."?=";
    $subject = "=?UTF-8?B?".base64_encode($subject)."?=";

    $headers = "From: $from_user <$from_email>
".
        "MIME-Version: 1.0" . "
" .
        "Content-type: text/plain; charset=UTF-8" . "
";

    return mail($to, $subject, $message, $headers);
}