need help ,php class and xml save load edit example.p

Question

http://www.sendspace.com/file/2zlfgn

I have the php files i been trying to get them to save to xml.

I have tried

$product1=array();
$product1['id'] = new product( "19990","modrl","maf","purpose","war");

only the ID writes to xml. since model, maf etc are sub-elements is there a different way to create the object array?