The Wonders of WordPress
Multisite

Patrick Johanneson
bona fides
➢ Web Coordinator at Brandon University
➢ Assisted with BU's first webserver, 1996(ish)
➢ Working with WordPress since v. 1.5 or so
➢ Doing dev work in WordPress Multisite since v.
3.0

What is Multisite?
● Multisite allows multiple virtual sites to be run
from a single WP installation (Codex Glossary)
● Prior to version 3.0, WordPress MultiUser was
required for this functionality
● With WordPress version 3.0, Multisite
functionality was rolled into WP's core

Why does BU use Multisite?
● BU has several faculties with many
departments within them
● Each faculty and department has a website
● Each website has its own coterie of editors
● With WP Multisite, this is easy to set up and
maintain

How does one set up Multisite?
● See the WordPress Codex "Create A Network"
page for a full explanation
● You need to edit your wp-config.php file...
● ...set up your Network in /wp-admin/...
● ...and then edit your wp-config.php and
.htaccess files again.
● Don't panic!

wp-config.php
define( 'WP_ALLOW_MULTISITE', true );
/* That's all, stop editing! Happy blogging. */

Tools > Network Setup

Network Setup

Network Setup complete

wp-config.php
define( 'WP_ALLOW_MULTISITE', true );
define( 'MULTISITE', true );
define( 'SUBDOMAIN_INSTALL', false );
$base = '/';
define( 'DOMAIN_CURRENT_SITE', 'example' );
define( 'PATH_CURRENT_SITE', '/' );
define( 'SITE_ID_CURRENT_SITE', 1 );
define( 'BLOG_ID_CURRENT_SITE', 1 );
/* That's all, stop editing! Happy blogging. */

Users in Multisite
● Each site in a Multisite installation can have its
own unique users, but all users are added to a
site-wide "pool" of users
● A user who is an Administrator on Site A can
be a Contributor on Site B, a Subscriber on
sites C and D, and have no privileges at all on
Site E
● Also, Multisite adds a new administrative level:
Super Admin, who can make network-wide
changes

Network Users list

Add New User -- "classic" vs. Multisite

Adding Sites
● The Super Admin(s) can add sites

Connecting Sites
● News and Events – Centralized or distributed?
● Parents and grandparents
– Breadcrumbs
– Contact information

News (Centralized)
● BU's news lives in the /news/ site, and is
maintained by a handful of people
● The news articles are categorized by site --
eg, news for the English homepage is in the
English category, news for Physics in the
Physics category, etc.
● Custom code fetches & displays the news for
each site in the BU network

Music Homepage

add_action( 'bu_news_region', 'bu_get_news' );
function bu_get_news() {
// Current site
$site_name = get_bloginfo( 'name' );
if( 'News' == $site_name ) return;
// no point doing anything *in* the News site
$cat_id = bu_get_category_from_site( $site_name );
$url = get_bloginfo( 'wpurl' );
// Some site details
$news_site = get_blog_details( 'News' );
$original_site = get_current_blog_id();
// so we can come back later
// switch to the news site
switch_to_blog( $news_details->blog_id );
// get the posts with category matching the site name
$args = array( 'category' => $cat_id, 'numberposts' => 4 );
$articles = get_posts( $args );

if( is_array( $articles ) && ! empty( $articles ) ) {
$article_list = "<h2>$site_name News</h2>";
$article_list .= '<dl>';
foreach ( $articles as $post ) {
setup_postdata( $post );
$article_list .= '
<dt>
<a href="' . get_permalink() . '">' . get_the_title() . '</a>
</dt>
<dd>
<span class="news-date">' . get_the_date() . '</span>
</dd>';
} // end foreach
$article_list .= '</dl>';
} // endif
switch_to_blog( $original_site );
if( strlen( $article_list ) > 0 ) {
echo( $article_list );
}
} // end of function

Events (Distributed (well, soon))
● BU is moving to tri.be's The Event Calendar,
which will allow site editors to maintain their
own events
● Events may be suggested for promotion by
site editors, so that they might appear on the
BU Home Page Event listing
● Promoted events must be authorized by a site
administrator

events.php Assumptions
The code that follows is the core of the event promotion
system. Several checks have been trimmed for brevity:
● Checking to ensure we're not in the root site (if we
are, bail out with a return; )
● The following must all be true:
– tribe_is_event()
– event is in the appropriate category in the sub-site
– there isn't already a promoted event for the given $id

add_action( 'save_post', 'bu_event_promote' );
function bu_event_promote( $id ){
if( ! isset($id) || ! is_numeric($id) ) { return(false); }
$from_site = get_bloginfo('name');
$from_site_id = get_current_blog_id();
// setup the required variables BEFORE we switch to the home site
$event_title = get_the_title( $id );
$event_url = get_permalink( $id );
$event_start = tribe_get_start_date( $id, false, 'Y-M-d' );
$event_end = tribe_get_end_date( $id, false, 'Y-M-d' );
switch_to_blog( BLOG_ID_CURRENT_SITE );
$args = array(
'post_status' => 'draft',
'post_content' => "This is a promoted post, from the '$from_site'
site.nPlease do not edit this post; just publish it if appropriate, or ignore
it.",
'post_title' => $event_title,
'EventStartDate' => $event_start,
'EventEndDate' => $event_end,
);
$new_event_id = tribe_create_event( $args );

// Meta info (redirection)
$meta = array(
'_pprredirect_active' => 1,
'_pprredirect_type' => 301,
'_pprredirect_rewritelink' => 1,
'_pprredirect_url' => $event_url,
);
$meta_unique = true;
foreach($meta as $key => $value){
add_post_meta($new_event_id, $key, $value, $meta_unique);
}
switch_to_blog( $from_site_id );
// back from whence you came
// once all that's done, add the _bu_promoted_event meta to the original $event
// using the new event's $post->ID so it can be removed later, if necessary
add_post_meta($id, '_bu_promoted_event', $new_event_id, true);
// All done
}

Site Parents & Breadcrumbs
● WordPress Multisite does not support nested
sub-sites (ie, /arts cannot contain /arts/english)
● /arts and /english are two separate sites
● With a bit of plugin magic, though, we can
set /arts as the parent site of /english, so that
breadcrumbs look like this:

Site Parent
● Arts is interposed in the breadcrumb via an in-
house plugin named Site Parent. Site Parent
sets an option in the current site with the ID of
the selected "Parent".

More Site Parent uses
● The Site Parent option is also used by the in-house
Contact Info plugin
● If the current site has no contact information set, the
plugin will look to the site's Site Parent, using
switch_to_blog()
● If there's no contact info there, the plugin ascends
level after level, until it gets to the root site
● If the root site's contact info is empty, the plugin
displays a default string

References
● Codex.WordPress.org
– Glossary
– Before You Create a Network
– Create a Network
– Function Reference (x1000)
– Plugin API pages (filters, hooks, etc)
● WordPress.org/support
● Tri.be support pages & forums
● WordPress.StackExchange.com

You've got questions,
I've got answers.
...hopefully.

fin.