XML expression using nodes and attributes - how do I check data is present?

[ninken11]

I have an expression for obtaining data from some XML:\[code\]$xml->children('aaa', true)->bbb->attributes()['ccc']\[/code\]What's the best way to check that the 'ccc' attribute and all leading nodes are present? I appreciate that \[code\]isset()\[/code\] is normally used in basic traversals, but I can't find a solution that takes attributes into account.