XML session

Hi. I'm trying to create a session support where i can keep persistent objects. I'm using XML to structure the data in the session file. But i've come into a problem. When i execute the following code the (-->>) marked instruction simply breaks the function execution: $sess = $xml->documentElement;

    -->>$sessIdElem = $xml->createElement(session_id());

$sessVarsElem = $xml->createElement("vars"); $sessVarsNode = $sessIdElem->appendChild($sessVarsElem); $sess->appendChild($sessIdElem); In the HTML output i get the following error: Exception thrown without a stack frame in Unknown on line 0 I read the docs on createElement and it doesn't throw exectpions... Can anyone tell me waht i'm doing wrong? Thanks!