This hook is called when composing the ACL to restrict access to civicrm entities (civicrm groups, profiles and events).
In order to use this hook you must uncheck "View All Contacts" AND "Edit All Contacts" in Drupal Permissions for the user role you want to limit. You can then go into CiviCRM and grant permission to Edit or View "All Contacts" or "Certain Groups". See the Forum Topic at: http://forum.civicrm.org/index.php/topic,14595.0.html for more information.
hook_civicrm_aclGroup($type, $contactID, $tableName, &$allGroups, &$currentGroups)
- $type - the type of permission needed
- $contactID - the contactID for whom the check is made
- $tableName - the tableName which is being permissioned
- $allGroups - the set of all the objects for the above table
- $currentGroups - the set of objects that are currently permissioned for this contact. This array will be modified by the hook
- null - the return value is ignored
Check HRD Module