Description:
------------
The documentation suggests the default value of the last parameter in the imap_open function is NULL.

imap_open ( string $mailbox , string $username , string $password [, int $options = 0 [, int $n_retries = 0 [, array $params = NULL ]]] ) : resource

However entering NULL as the value for that parameter produces the following error:

imap_open() expects parameter 6 to be array, null given

Test script:
---------------
imap_open('{imap.example.com:993/imap/ssl}INBOX', 'username', 'password', 0, 0, null);

Expected result:
----------------
Based on the documentation, it should allow NULL as a value. Otherwise the documentation should be changed to show this parameter as an empty array.