<?php
$startsession_xml=simplexml_load_string($xml_result);

//parse sessionid form the returned xml, ot be used in the call to send message
$this->sessionid    =   $startsession_xml->sessionID;

print_r($this->sessionid);
?>

SimpleXMLElement Object
(
    [0] => db1ebcd550b15bcf22b5e3efc903c8b3
)