<?PHP
error_reporting(E_ALL );
    ini_set('display_errors',1);

$t =<<<D
<form id="frm-send" method="post"   action="index.PHP"   >
<input type="text" name="data[postusername]" id="postusername" value="user"  />    
<input type="checkBox"  name="data[save]" id="data[save]" value="1" />   
<input type="hidden" name="secret" id="secret" value="0d35635c0cb11760789de6c4fe35e046311f724b" />
<input type="submit" name="btnSubmit" id="btnSubmit" value="Send"  />   
<input type="hidden" name="data[checkgetrequest]" value="true" id="data[checkgetrequest]" />
<input type="hidden" name="frm-id" value="13448477965028bfb44222d" id="frm-id" />
</form>
<input type="text" id="getfocus_txt_13448477965028bfb44222d" name="getfocus_txt_13448477965028bfb44222d" />


D;
    $dom = new domDocument;
    $dom->loadHTML($t);
    $dom->preserveWhiteSpace = true;
    $frmid = $dom->getElementById('frm-id') ;
    echo  $frmid->getAttribute('value');


?>

它显示了一个错误：

Fatal error: Call to a member function getAttribute() on a 
non-object in E:\Apache\msg.PHP on line 22

我在Windows 7上使用XAMPP 1.7.3.
我在我的服务器上测试了它,它显示我没有错误.
任何帮助,将不胜感激.