iphone sdk推送通知随机失败

我有一个包含以下内容的php文件,它在开发证书上运行得很好,但是当我切换到生产证书时,php会出错并给出下面的消息,但它只在大约50%的时间内这样做。其他50%都能用。有人知道为什么会这样吗?

<?php
// masked for security reason 
$deviceToken = 'xxxxxx'; // jq

$ctx = stream_context_create();
stream_context_set_option($ctx, 'ssl', 'local_cert', dirname(__FILE__)."/prod.pem");

$number = 5;

$fp = stream_socket_client('ssl://gateway.push.apple.com:2195', $err, $errstr, 60, STREAM_CLIENT_CONNECT, $ctx);
if (!$fp) {
  print "Failed to connect $err $errstr\n";
}
else {
  print "Connection OK\n";
  $msg = $_GET['msg'];
    $payload['aps'] = array('alert' => $msg, 'badge' => 1, 'sound' => 'default');
    $payload = json_encode($payload);

  $msg = chr(0) . pack("n",32) . pack('H*', str_replace(' ', '', $deviceToken)) . pack("n",strlen($payload)) . $payload;
  print "sending message :" . $payload . "\n";
  fwrite($fp, $msg);
  fclose($fp);
}
?>

php错误:

警告:stream_socket_client()[函数.stream socket client]:无法设置本地证书链文件`/var/www/vhosts/thissite.com/httpdocs/prod.pem';请检查cafile/capath设置是否在/var/www/vhosts/thissite.com/httpdocs/pushMessageLive.p中包含证书及其颁发者的详细信息HP在线19

警告:stream_socket_client()[函数.stream socket client]:未能在第19行的/var/www/vhosts/thissite.com/httpdocs/pushMessageLive.php中创建SSL句柄

警告:stream_socket_client()[函数.stream socket client]:无法在/var/www/vhosts/thissite.com/httpdocs/pushMessageLive.php的第19行启用加密

警告:stream_socket_client()[函数.stream socket client]:无法连接到/var/www/vhosts/thissite.com/httpdocs/pushMessageLive.php中的ssl://gateway.sandbox.push.apple.com:2195(未知错误),位于第19行 无法连接0