XML Parsing Error: xml declaration not at start of external entity

Posted on 2007-11-22
Last Modified: 2008-02-01
im building my own trackback class for my personal blog.

when i try calling my trackback URL like this: http://localhost/my-blog/this-is-a-test-entry/trackback/  i get the following error:

XML Parsing Error: xml declaration not at start of external entity
Location: http://localhost/my-blog/this-is-a-test-entry/trackback/
Line Number 1, Column 2: <?xml version="1.0" encoding="UTF-8"?>

when i look at the source code, i dont have any whitespaces.  i have checked every line of my code over and over again incase i missed one hiding...

i searched on the web and read that a 8-bit character can be inserted infront of the XML declaration tag but i dont know how it could have?

if i create another example like below it works fine...

function test()
      $xmlWrite = '';
      $xmlWrite .= "<?xml version=\"1.0\" encoding=\"utf-8\" ?>";
      $xmlWrite .= "<test>";
      $xmlWrite .= "<success>works fine...</success>";
      $xmlWrite .= "</test>";
      return $xmlWrite;

header("Content-type: text/xml");
echo test();

please see my original code below.  I know most of this is PHP so ive included this question in the PHP zone too...
trackback.php - the page that is called when user requests :


header("Content-type: text/xml");

$host = trim($_SERVER['HTTP_HOST']);

if(substr($host,0,4) == 'www.')


	$host = substr($host,4);


$now = date('Y-m-d G:i:s');

$ip = trim($_SERVER['REMOTE_ADDR']);

$agent = trim($_SERVER['HTTP_USER_AGENT']);

$domain = 'http://www.'.trim($host).'/';


$trackback = new Trackback('','','UTF-8');

global $response, $comment;

$tb_id = trim($HTTP_GET_VARS['id']);

$tb_title = trim($HTTP_POST_VARS['title']);

$tb_blog_name = trim($HTTP_POST_VARS['blog_name']);

$tb_url = trim($HTTP_POST_VARS['url']);

$tb_content = substr($HTTP_POST_VARS['excerpt'],0,2000);

$permalink = $domain;



	$err_response = 'XML-RPC server accepts POST requests only.';


// do a few checks to see if trackback is spam or already in table etc etc



	echo trim($trackback->recieve(false,$err_response));




	echo trim($trackback->recieve(true,''));



class.trackback.php recieve function:

 function recieve($success = false, $err_response = "") 


        if (!$success && empty($err_response))


            $err_response = "An error occured while tring to log your trackback...";



		$return = '<?xml version="1.0" encoding="utf-8"?>'."\n";

        $return .= '<response>'."\n";


		if ($success) 


            $return .= '    <error>0</error>'."\n";




            $return .= '    <error>1</error>'."\n";

            $return .= '    <message>'.$this->xml_safe($err_response).'</message>'."\n";



        $return .= '</response>';

        return $return;


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Question by:ellandrd
  • 2

Accepted Solution

nitinsawhney earned 500 total points
ID: 20333673

Looks like a header conflict in your code.

Just remove header("Content-type: text/xml"); from your code and it should do the trick.
If it doesn't work then add another "\n" to following line in the function receive
 $return = '<?xml version="1.0" encoding="utf-8"?>'."\n\n";

LVL 16

Author Comment

ID: 20333686
ok after removing the header i dont get the above error,but if i view source i still get that whitespace or 8-bit char shown up...
 <?xml version="1.0" encoding="UTF-8"?>



    <message>You didnt post an id to apply the trackback to...</message>


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LVL 16

Author Comment

ID: 20335875
I completely rewrote the whole class and now it works fine this time...

thanks for the time and help


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