Free Working With MediaWiki by Yaron Koren

information about all the visitors to that page; which would be a violation of privacy. You can change this default by adding the following to LocalSettings.php:
$wgAllowExternalImages = true;
    If this is set, placing the URL of an external image in a page will display that image there.
    You can also, instead, use the variable $wgAllowExternalImagesFrom to only allow images from certain trusted domains. Here is one example:
$wgAllowExternalImagesFrom = array( 'http://upload.wikimedia.org', 'http://www.flickr.com' );
    However, if you’re planning to use images from Wikimedia Commons (whose URL always starts with upload.wikimedia.org), the best approach is to use the “InstantCommons” feature — which lets you directly use the standard image syntax to display images found on Wikimedia Commons. If you have InstantCommons enabled, and have a call that looks like “
[[Image:Rocking horse.jpg|...]]
”, MediaWiki will first look for an image named “Rocking horse.jpg” on your wiki; and, if it doesn’t find one, will look for that file name on Wikimedia Commons, and display that one if it finds it there. You can enable InstantCommons by adding the following to LocalSettings.php:
$wgUseInstantCommons = true;

8  User registration and management
Registration
    By default, user registration in MediaWiki is fairly simple: for users who are not logged in, at the top of each page is either (for MediaWiki 1.20 and up) two links, reading “Create account” and “Log in”, or one link reading “Log in / create account”. It’s a fairly small difference, since each of those two pages links to the other anyway.
    If you click on either “Log in” or “Log in / create account”, you’ll see a screen that looks like Figure 8.1.
    Figure 8.1 Login screen
    If you click on the “Create account” link, either from this screen or (if it’s there) from the top of any page, you’ll see something like Figure 8.2.
    Figure 8.2 “Create account” screen
    There is no demographic or questionnaire information solicited; just the essential fields of username and password, plus optional fields for email address and real name. And if you have the anti-spam ConfirmEdit extension installed (see here ), you will probably also see some form of CAPTCHA there.
    The email address field is recommended for all users to fill in, since it allows for notification and messaging. As an administrator, you can require users to enter and confirm an email address before they can read or edit on the wiki, if you want, by using the “emailconfirmed” group (see next section).
    What about the “Real name” field? That’s not a very important field, but it can be nice to fill in if your username is different from your real name, but you still want people to know what your real name is. Other users can view it if they go to the “action=credits” URL for a specific page (this has to be typed in manually; it’s not linked from anywhere). On Wikipedia and other Wikimedia sites, this action is disabled, for privacy reasons. (Most likely the disabling was done using the $wgActions setting.)
    There are also various extensions that allow for displaying real names in different formats; you can see listing of these extensions here:
    https://www.mediawiki.org/wiki/Category:Real_name_display_extensions
    If, as an administrator, you want users to fill in more information about themselves when they register, there’s at least one extension that allows that: SemanticSignup, which also requires the Semantic MediaWiki and Semantic Forms extensions. You can read more about SemanticSignup here:
https://www.mediawiki.org/wiki/Extension:SemanticSignup
    Another extension, ConfirmAccount, requires potential users to fill in more information about themselves — for the purpose of getting approval to become a user. See here for more detail.
Usernames
    In general, MediaWiki is very flexible about the username users can choose — it can include nearly any Unicode