特殊字符的 APNS 问题

我在发送抛出 APNS 的消息时遇到一些问题，这些消息包含特殊字符，如 É 。可能出了什么问题？请自己尝试一下，如果有人知道问题，请给我一个答案。谢谢。我有一个 php 脚本来完成这项工作

<?php
// Put your device token here (without spaces):
$deviceToken = 'XXXXXXXXXXXXXXXXXXXXXXXXXXX';
// Put your private key's passphrase here:
$passphrase = 'XXXXXXXX';
// Put your alert message here:
$message = 'É';
////////////////////////////////////////////////////////////////////////////////
$ctx = stream_context_create();
stream_context_set_option($ctx, 'ssl', 'local_cert', 'ck.pem');
stream_context_set_option($ctx, 'ssl', 'passphrase', $passphrase);
// Open a connection to the APNS server
$fp = stream_socket_client(
    'ssl://gateway.sandbox.push.apple.com:2195', $err,
    $errstr, 60, STREAM_CLIENT_CONNECT|STREAM_CLIENT_PERSISTENT, $ctx);
if (!$fp)
    exit("Failed to connect: $err $errstr" . PHP_EOL);
echo 'Connected to APNS' . PHP_EOL;
// Create the payload body
$body['aps'] = array(
    'alert' => $message,
    'sound' => 'default'
    );
// Encode the payload as JSON
$payload = json_encode($body);
// Build the binary notification
$msg = chr(0) . pack('n', 32) . pack('H*', $deviceToken) . pack('n', strlen($payload)) . $payload;
// Send it to the server
$result = fwrite($fp, $msg, strlen($msg));
if (!$result)
    echo 'Message not delivered' . PHP_EOL;
else
    echo 'Message successfully delivered' . PHP_EOL;
// Close the connection to the server
fclose($fp);

它能有什么问题？