From Facebook Developers Wiki

Returns count of object ids that are associated with specified object. This function takes constant time to return the count, regardless how many objects are associated.

Contents 1 Parameters 2 Return Value 3 PHP Client Coding Examples 4 FQL Equivalent 5 Error codes

[edit] Parameters

Type	Name	Description
string	api_key	The application key associated with the calling application.
string	session_key	The session key of the logged in user.
float	call_id	The request's sequence number. Each successive call for any session must use a sequence number greater than the last. We suggest using the current time in milliseconds, such as PHP's microtime(true) function.
string	sig	An MD5 hash of the current request and your secret key, as described in the authentication guide.
string	v	This must be set to 1.0 to use this version of the API.
string	format	Optional - desired response format. Either "XML" (default) or "JSON".
string	callback	Optional - wrap the response inside a function call. This is primarily to enable cross-domain javascript requests using the <script> tag, sometimes known as "JSONP". This works with both XML and JSON.
string	name	Name of the association.
int64	obj_id	Object identifier.

[edit] Return Value

integer: count of associated objects of the specified object. Seems to be returning empty string for zero.

[edit] PHP Client Coding Examples

[edit] FQL Equivalent

(none)

[edit] Error codes

Code	Description
1	An unknown error occurred. Please resubmit the request.
2	The service is not available at this time.
4	The application has reached the maximum number of requests allowed. More requests are allowed once the time window has completed.
5	The request came from a remote address not allowed by this application.
100	One of the parameters specified was missing or invalid.
101	The api key submitted is not associated with any known application.
102	The session key was improperly submitted or has reached its timeout. Direct the user to log in again to obtain another key.
103	The submitted call_id was not greater than the previous call_id for this session.
104	Incorrect signature.
200	Permission denied. Calling application or user doesn't have enough permissions to perform the action.
800	Internal error. Please report this to Facebook when getting this error.
801	Invalid operation error. This operation is not allowed.
802	Quota exceeded. Certain maximum number allocated for an application or a user is exceeded.
803	Requested object is not found on server.
805	A temporary database failure happened. Usually this can be corrected by a re-try.