Elgg API

I am trying to use the elgg api.

When I call the method in a browser directly, everything is fine


but when I try to call this method in a script from another Server using file_get_contents, something like that returns:

<?xml version='1.0' encoding='UTF-8'?>

<status type="integer">
<message type="string">
Unable to save new object's base entity information!</message>

What's wrong here?