Manual:Hooks/ChangeTagsAllowedAdd

Details

 * : Array of all the tags the user is allowed to add. Any tags the user wants to add (in, the next parameter) that are not in this array will cause it to fail. You may add or remove tags to this array as required.
 * : Array of tags user intends to add.
 * : User who is adding the tags, or  if checking for a generic non-blocked user with the relevant rights.