add http headers

Hi,

Do I need to add header("Content-type: text/xml");to my script or somewhere in my site in order to parse XML? If so, how do I go about doing that?

code snippet that requires the header:

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

$dom = new DOMDocument("1.0");
$node = $dom->createElement($wpdb->prefix.'address_table');
$parnode = $dom->appendChild($node); 

 $node = $dom->createElement("marker");
		  $newnode = $parnode->appendChild($node);
		  $newnode->setAttribute("lat",$data->results[0]->geometry->location->lat);
		  $newnode->setAttribute("lng", $data->results[0]->geometry->location->lng); 

echo $dom->saveXML();

This is the error I get:
error on line 7 at column 45: Entity ‘raquo’ not defined