XML : complex XML to array in codeigniter

I am getting complex XML as a response i need to convert in to an array, here is my sample complex XML

     <?xml version="1.0" encoding="UTF-8"?>   <Response xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">      <SearchResult>    <Result>       <aaa>string</aaa>       <bbb>string</bbb>       <ccc>          <ddd>             <eee>string</eee>             <fff>string</fff>          </ddd>          <ddd>             <eee>string</eee>             <fff>string</fff>          </ddd>       </ccc>       <ggg>          <hhh>             <iii>string</iii>             <eee>string</eee>             <jjj>string</jjj>            </hhh>          <hhh>             <iii>string</iii>             <eee>string</eee>             <jjj>string</jjj>            </hhh>       </ggg>       <kkk>          <hhh>             <iii>string</iii>             <eee>string</eee>             <jjj>string</jjj>            </hhh>       </kkk>       <lll>          <mmm>string</mmm>          <nnn>string</nnn>          <ooo>string</ooo>         </lll>      </Result>          <Result>     //same values as above       </Result>         <Result>     //same values as above      </Result>        </SearchResult>    </Response>    

I have tried simple XML but its not working,

      function xml2Array($xmlstring)  {      $xml = simplexml_load_string($xmlstring, "SimpleXMLElement", LIBXML_NOCDATA);      $json = json_encode($xml);      return json_decode($json,TRUE);  }    $arr = xml2Array($response);  print_r($arr);    

But it returns empty array please suggest with possible solution for this