使用PHP simplexml_load_string函数变量更新MongoDB，将额外的'0'键添加到值

I have a script that is attempting to update a MongoDB collection with an xml response I've received from a server. I'm envoking simplexml_load_string() on the response. However, when updating the fields, it's adding an extra '0' key to the value I'm attempting to add. Here is the code:

$xml = simplexml_load_string($response);
if($xml->type == "reject") {
    $status = $xml->type;
    $message = $xml->message;
}
$update = array('$set' => array('status' => $status, 'response' => $message));

This is what I'm expecting:

{ "_id" : ObjectID("..."), "status" : "reject", "response" : "The message." }

However, here is the entry that is being saved in MongoDB:

{ "_id" : ObjectID("..."), "status" : { "0" : "reject" }, "response" : { "0" : "The message." } }

Any idea what is happening, or suggestions on how to fix it? Thanks!

$xml->type and $xml->message are probably objects, not strings. You might want to var_dump it to see what it actually is and then convert it to a string.