标题“警告:无法修改标题 -”，但也具有移动重定向脚本

我尝试在网站上搜索"警告：无法修改标头信息 - 标头已发送(输出始于/home/zenithda/public_html/www.thanow.com/index.php：12(在第 52 行的/home/zenithda/public_html/www.thanow.com/index.php。

查看了其他示例，但我找不到与我的问题相似的示例。我正在为我的网站的移动版本运行移动重定向脚本。我还有一个页眉.php和页脚.php在我的包含文件夹中运行。但是，当我尝试通过我的安卓设备访问我的网站时，我会收到上述警告。有人试图检查他们的iPhone，同样的事情发生了。在警告下方，将显示网站的桌面版本。在我的索引.php中，这是直接显示在我的第一个命令上方的代码(这个论坛不允许我正确显示此代码之前的内容，所以，这里有代码"！文档类型 Html，大约三行！如果IE7,8,9行，一个HTML头，一些元字符集="utf-8"标题和元描述和关键字。ALSO = PHP 命令之前没有空格。

<?php

  //Load the Mobile Detection library
  include("js/mobiledetect.php");
  //In this simple example, we'll store the alternate home page file names.
  $iphoneTierHomePage = 'mobile/index.html';
  $genericMobileDeviceHomePage = 'mobile/index.html';

  //Instantiate the object to do our testing with.
  $uagent_obj = new uagent_info();

  //This is a common mobile detection scenario...
  // First, detect iPhone tier devices, like iPod Touches, Android, WebOS, etc. 
  //    Send them to the nice touch-optimized page. 
  //    These often have rich CSS and advanced but mobile-friendly JavaScript functionality and no Flash.
  // Second, detect any other mobile device. Send them to the basic mobile pages, with light CSS and no JavaScript.
  //    Some (often older) touch devices might be included in this bunch, which otherwise includes feature phones.
  //    It's a Best Practice to include an alternate web page for less-capable mobile devices. 
  // Finally, assume anything else not caught by these filters is a desktop PC-class device. 
  //    Send them to your regular home page which may include large pictures, lots of JS, Flash, etc.. 
  //
  // NOTE: If you wanted an iPad-class tablet-optimized web site, too, then you should FIRST do a 
  //    device detection using the DetectTierTablet() method. Then detect for iPhone tier, and so on. 

  //In this simple example, we simply re-route depending on which type of device it is.
  //Before we can call the function, we have to define it. 
  function AutoRedirectToProperHomePage()
  {
      global $uagent_obj, $iphoneTierHomePage, $genericMobileDeviceHomePage;
    //We have variables for certain high-usage device variables, like the iPhone Tier.
    //   You might use the device variables to show/hide certain functionality or platform-specific features and ads, etc.
    //   Alternately, you can use the method: DetectTierIphone().
    //   Sometimes, you may wish to include the Tablet Tier devices here, as well. 
      if ($uagent_obj->isTierIphone == $uagent_obj->true) 
      header ('Location: '.$iphoneTierHomePage);
    //We can generally use the Quick Mobile detection method to save a couple of cycles.
      else if ($uagent_obj->DetectMobileQuick() == $uagent_obj->true) 
      header ('Location: '.$genericMobileDeviceHomePage);
    //We'll assume that anything else not caught in the above filters is a desktop-class device. 
    //   (Which can include tablets.)
    }
  //Now, we can call the redirect function.
  AutoRedirectToProperHomePage();
?>

之后是这一行：

    <?php include 'includes/header.php' ?>