Manipulation of XML in PHP

I have an API call which returns a XML string, I have converted that response with new SimpleXmlElement so that it returns me a XML object. Below is the result

SimpleXMLElement Object
(
    [0] => <root>
                <PINCODELIST>
                    <PINCODE>152001</PINCODE>
                    <CITYNAME>GURDASPUR</CITYNAME>
                    <ACTIVEFLAG>Y</ACTIVEFLAG>
                    <EDIT_DATE>09 May 2015 10:47:20</EDIT_DATE>
                    <ROUTINGCODE>N/PB/1026/FRZPR</ROUTINGCODE>
                </PINCODELIST>
            </root>
)

How do I access each element in root tag assuming it can have X number of PINCODELIST tags.

I tried $res[0]->root but it gaves me SimpleXMLElement Object ( )

Any ideas ?