URGENT parsing xml file using codeigniter?

[eluser]Musaddiq Khan[/eluser]
I have tried the foloowing code.

Code:

$xml = file_get_contents($xmlfile);
$this->load->library('simplexml');
$xmlData = $this->simplexml->xml_parse($xml);

But it givs the error.

Unable to load the requested class: simplexml

Is it needed to download this library or it is builtin class in codeigniter libraries.
Thanx