This hooks gives modules a chance to handle the user authentication (for example to authenticate against an external source like an LDAP server).
Call time:
Just before Phorum runs its own user authentication.
Hook input:
An array containing the following fields:
Hook output:
The same array as the one that was used for the hook call argument, possibly with the user_id field updated. This field can be set to one of the following values by a module: