How do you use a @ symbol in the name of a PHP object

[CiOooo]

I've got an XML file that has the label @attributes for one of the names\[code\]SimpleXMLElement Object( [@attributes] => Array ( [PART_NUMBER] => ABC123\[/code\]I want to make a reference to this object like $product->@attributes['part_number'] but of course the @ symbol causes an error.So how do I reference this item in the object?