sugarCRM add document from script

sugarCRM add document from script

I am trying to add Document to Sugar object (client) from PHP script. I
have a directory of files (on the same server where sugarCRM is installed)
and xls with sugar objec ID and filename). PHP Script should add correct
filename to specific sugar object (identified with ID). I can read XLS
this is no problem, I can also get instance of sugar object (retrieve by
ID), but I have no idea how can I assign the file to sugar. I was trying
with Document, and upload_file.php, but those seem to be usable with
uploading single file with html Form.
How can I automate this task, copy files with correct filename to
cache\upload and create Document related to my Customer from PHP Script? I
would prefer not to use SOAP if it's not necesarry...