Webservice with php/soap

Hi there, i'm working on php/drupal to establish a soap connection,and make some operations. For now i can - obtain a token - create afolder - read a folder (obtain a list of nodes) but i try to createa document with createDocument function. the document is created, buteach time is empty. Is anybody have a sample for xml mine is this oneand i don't understand why my file is empty !!