Bad parse with tag <?xml ?>

[serako]

Hi,
I try to use this parser for change a gpx file.
The first line is :
<?xml version="1.0" encoding="UTF-8"?>...other tag ...
but after simple parse :

$dom = new Dom;
$dom->load($gpx);
return $dom->outerHtml;

$gpx is in text format

the result is :
<?xml version="1.0" encoding="UTF-8">...other tag ...<?xml>

I use the package 2.2.1 in laravel 6.