Missing user password with REST Api parsing on facebook user connection

I am trying to implement a Facebook login under a Symfony2 project using the parse.com REST Api.

Here is the code I am using to call CURL:

$headers = array(
"Content-Type: application/json",
"Content-Length: " . strlen($facebookJson),
"X-Parse-Application-Id: " . $applicationId,
"X-Parse-REST-API-Key: " . $parseRestAPIKey
);

$handle = curl_init(); 
curl_setopt($handle, CURLOPT_URL, $url);
curl_setopt($handle, CURLOPT_HTTPHEADER, $headers);
curl_setopt($handle, CURLOPT_SSL_VERIFYPEER, false);
curl_setopt($handle, CURLOPT_RETURNTRANSFER, true);
curl_setopt($handle, CURLOPT_POSTFIELDS, $facebookJson); 

$data = curl_exec($handle);
curl_close($handle);

      

        
        
        
      

    

The variable $facebookJson

represents authData:

{
  "facebook": {
    "id": "user Facebook id number as a string",
    "access_token": "an authorized Facebook access token for the user",
    "expiration_date": "token expiration date of the format: yyyy-MM-dd'T'HH:mm:ss.SSS'Z'"
  }
}

      

        
        
        
      

    

In this example, the user is not a logged in user in the parsing, so he must create a new user (as stated in the documentation ), but instead of creating a new user, the following error message appears:

"{" code ": 201," error ":" missing user password "}

Since I'm using Facebook to register a user, I don't think it should ask for a password, the documentation doesn't mention it.

Any suggestions to fix this issue?

Should I try another approach to inject Facebook login using parsing? (maybe it is easier, for example with parse javascript sdk).