Problem parsing large XML file

[admin]

Hi,
I've been trying trying to parse a 16Mb XML file using simpleXML.
I'm using the following code:

$xml_data = simplexml_load_file('ProductFeed.xml');
foreach ($xml_data->product as $product) {
$advertiser = $product->Advertiser;
echo $advertiser;
}
The code works on small XML files, however when I use it to try and parse the 16Mb file it returns the following error:
INTERNAL SERVER ERROR

An internal server error has occured!
Please try again later.

Can anyyone help me parse this file??

Thanks