SimpleXMLElement parsing issue with PHP

[Teegrerne]

I'm trying to parse out the following response:SimpleXMLElement Object ( [responseType] => SimpleXMLElement Object ( [inputConceptName] => aspirin [inputKindName] => % ) [groupConcepts] => SimpleXMLElement Object ( [concept] => Array ( [0] => SimpleXMLElement Object ( [conceptName] => ASPIRIN [conceptNui] => N0000145918 [conceptKind] => DRUG_KIND ) [1] => SimpleXMLElement Object ( [conceptName] => Aspirin [conceptNui] => N0000006582 [conceptKind] => INGREDIENT_KIND ) ) ) ) in PHP. I have it stored as a curl string:\[code\]$xml = simplexml_load_string($data);print_r($xml);\[/code\]How do I get just the conceptNui of the first object as a PHP variable?Thanks!