Where is the xml file coming from? Are you pulling it off another website or uploading it? How do you mean you have not be able to do this instead SS? All you have to do is make a function in your Page class (or Page_Controller depends on what you need to do).

Example of loading a file and outputting it

mysite/code/Page.php inside Page_Controller class

Then you can call this in your code with $this->readxml() or via URL - yoursite.com/home/readxml.

Hello it's me again!... Now I have other question, where should I place my xml files. First I put them in a directory in the assets directory, but I couldn't figure out how to reference them I mean I was using something like this

$file = file_get_contents("\assets\XMLFiles\ABIfir.xml") but it doesn't find the file. The debug error says "failed to open stream: No such file or directory"

I have tried placing the file everywhere in my SS directory and nothing. It could be such a dummy thing to ask but I don't know where to place the files nor how to reference them.
Thanks again;

I tried this and didn't work either!
I tried specifying the whole path like this: file_get_contents("http://localhost/SilverStripe/assets/XMLFiles/ABIfir.xml") it woks fine.
How could I make it a relative path, to my root directory I mean "http://localhost/SilverStripe".
Thanks for your help!

Hello again!!
Thanks for the advice alirobe. My problem was basically that I was trying to use a relative path instead of the complete path "http://localhost/SilverStripe/assets/XMLFiles/ABIfir.xml". It works fine now, I will make look for a way to make it a relative path, but it works fine for now.
I'm getting my xml file using PHP simplexml, then I convert it into a array and from the array into a SS DataObjetSet to use it in my template.
I'm posting my function to convert xml

Public function convertXml2Array($obj, &$arr)
{
$children = $obj->children();
foreach ($children as $elementName => $node)
{
$tag= strtolower((string)$elementName);
$text = (string)$node;
$text = trim($text);
$arr['product'][$tag] = $text;

$arr['product']['children'] = array();
$this->convertXml2Array($node, $arr['product']['children']);
}
return;
}

Then I convert the array into SS DataObjectSet that I can use in my template. It works fine.