SimpleXMLElement cannot be found when working with namespaces

I’m trying to create a Widget in WordPress, and I’m running into an issue creating a SimpleXMLElement object.

Here is the code:

namespace GenieKnows_Search;  

class GenieKnows_Search_Widget extends WP_Widget {
     //Constructor
     function __construct() {
         parent::__construct('genieknows_search_widget', 'GenieKnows_Search_Widget');
     }

     //Irrelevant Code. Removed for readability. 

    //Return the XML
    function retrieve_gk_xml() {
          $xml = new SimpleXMLElement($this->create_gk_xml(), 0, true); //Line 114
          return $xml->xpath('/feed/results/sponsored/listing');
    }
}

Here is the error:

PHP Fatal error: Class ‘GenieKnows_SearchSimpleXMLElement’ not found
in
/var/www/myticketpick.com/wp-content/plugins/genieknows-search/genieknows_search.php
on line 114

It would appear that it’s trying to look for the SimpleXML class inside of my GenieKnows_Search namespace, however I’m at a loss as to why.

Any ideas on why this error is occurring, and how I can fix it?