docs.getDownloadUrl - not work as POST request, only as GET request

[anna.br...@gmail.com]

In our site there is a POST curl request to scribd where all parameters except api_key was sent in CURLOPT_POSTFIELDS. And it worked fine. But now the curl request return error "Required parameter missing". When I added all parameters to request url (CURLOPT_URL)- it works again. Can you please explain what could change? Why it stopped working as before?