Multisite & Beyond - WordCamp Baltimore 2012

Editor's Notes

1. WordPress Multi-Network is basically WordPress Multisite squared. Where the idea of WordPress Multisite is to set up multiple instances of WordPress sites within a single installation, the idea of WordPress Multi-Network is to set up multiple instances of WordPress Multisite within a single installation.
2. To think about the concept in everyday terms, consider a single WordPress instance as a single-family house. As the owner of the home (outside of a homeowner’s association), you have complete control over what happens to your home and land.
3. If you want to paint your siding yellow and your shutters blue, you can. Likewise, if you want to install a yellow and blue theme on your WordPress site, you have that ability, too.If you want to install a geothermal climate control system, a new hot water heater and a security/alarm system, you are allowed to do so and are responsible for doing so. With WordPress, if you want to install a plugin that allows you to share podcasts, a caching plugin and a security plugin, you have that ability.In a single-family home, you’re more than likely responsible for maintaining your own driveway, getting someone to remove the snow from around your house, managing trash removal, etc. You’re also responsible for keeping your own WordPress site up-to-date and keeping it clear of excess spam.Finally, if your house catches on fire or someone breaks in and steals all of your belongings, that’s also your responsibility. In WordPress, if your website takes down the Web server or someone hacks your site, that’s ultimately your problem, too.
4. WordPress Multisite is analogous to moving into a rowhouse or townhouse. You still own the home, but you have a little less control (and therefore, a little less responsibility) for what happens to your home.When living in a rowhouse or townhome, if your house catches on fire, that can spell serious trouble for your neighbors, as well. When working on a site within a network on WordPress, anything that happens to your site may also affect your neighbors (the other sites in the network).
5. You might be able to paint your siding and your shutters, but you’re probably at least going to have to get permission from your property manager. You can probably install your own heating and air conditioning and you can probably also put in your own security system. However, in all of these situations, you might have to use the company that already has a contract with the community. At the same time, though, it’s likely that you no longer have to worry about trash removal or snow clearing. Those are probably handled by the property manager.Likewise, on your WordPress site, you can use your own theme and activate many of your own plugins, but you’ll have to get the Super Admin to make those items available to you. Some things will be handled on a global level for all sites (for instance, a spam-control plugin like Akismet may very well be active on the entire network) and some things will be configurable on a site-by-site basis. You will probably have complete control over any settings and configuration changes that need to happen on your site, but the plugins and themes that are available will have to be installed by the Super Admin. In addition, as the site owner, you are no longer responsible for keeping WordPress or its plugins and themes up-to-date. Instead, that responsibility falls on the Super Admin for the Multisite installation (also known as a “network”).
6. WordPress Multi-Network puts another level on top of the normal Multisite setup. Instead of a single set of townhomes, you’re now talking about a subdivision of townhomes. There are now three levels of accountability for anything that happens within your home: your own responsibilities, the responsibilities of your row of townhomes and the responsibilities for the entire subdivision.
7. The Uber Super Admins (or whatever you want to call the people that manage the entire installation) are now responsible for installing plugins and themes and for keeping WordPress up-to-date. With a little bit of modification to the installation, they have the power to activate plugins and enable themes for the entire system. They are also ultimately responsible for keeping WordPress up-to-date.The normal Super Admins (the ones who are only Super Admin for one or a handful of networks in the installation) have a little bit less responsibility (and, again, with a slight modification, can have a little less power). They have the ability to network-activate plugins and network-enable themes, they have the ability to install plugins and themes, and they have control over the settings for the network.Finally, the Site Admins (the ones who are responsible for a single site within a network) have the same basic abilities and responsibilities they had in the Multisite setup.
8. The technical explanation is actually fairly simple. When WordPress Multisite is set up, a few extra tables are added to the database. One of those tables is the “site” table. In a normal WordPress Multisite installation, that table only ever has a single row. That row gets an ID of 1, which is then used to identify that “site” (in the old WPMU lexicon – now known as a “network” in WordPress Multisite) in the “sitemeta” and “blogs” tables. The “sitemeta” table is where network-wide options are stored; the “blogs” table is where a list of all of the “blogs” (in the old WPMU lexicon – now known as “sites” in WordPress Multisite) that have been created. Both of those tables have a “site_id” column to identify with which network they correspond.
9. Again, in a normal WordPress Multisite installation, there will only ever be one network, so that number will be “1” in all instances.However, with a slight modification, WordPress can be configured to start actually using that “site_id” to differentiate between networks.
10. To enable Multi-Network, you simply need to install and activate a single plugin. There are three different options:Networks for WordPress by David Dean – This plugin was initially developed for WordPressMU. It was then temporarily discontinued when WordPressMU merged into the WordPress core at 3.0.WP Multi Network by John James Jacoby – If, for some reason, you are running a version of WordPress between 3.0 and 3.2, you should use this plugin. This plugin is a branch of the plugin mentioned above that was made to be compatible with WordPress 3.0. If your WordPress installation is up-to-date, though, you should not use this plugin.Networks+ by Ron and Andrea Rennick – This is a premium plugin (you purchase the user manual and get the plugin with it) that enables WordPress Multi-Network. This plugin is a little bit more efficient, but also has fewer configuration options, than the other two plugins mentioned.Each of these plugins comes with fairly detailed instructions for enabling the new features. As with enabling multisite, enabling multi-network requires some changes to your wp-config.php file and to your file structure.It is vitally important that you follow those instructions, and that you get a copy of the current instructions (for the first two plugins mentioned above, there are a lot of different sets of instructions floating around the Web, and most of the older entries are terribly inaccurate when it comes to the latest versions of the plugins).
11. WordPress Multi-Network adds a third level of control, as well as a third level of architecture to your WordPress installation.
12. You can configure it in two basic ways:Networks as subdomains, sites within those networks as subdirectory sitesNested subdomains (single subdomains as the networks, second-level subdomains as the sites)Essentially, when you first set it up, you have to choose one of those two configurations (actually, when you set up multisite in the first place, you have to decide whether it will be a subdomain or subdirectory installation – that will carry over to all of your networks in multi-network).However, if you want to use unique domains for some networks, you can do so after you get things initially configured. For instance, if you have your installation set up to use nested subdomains, you could instead use a unique domain for each network, and use subdomains for each site in that network.In fact, if you configure everything properly, you can even use unique domains for each site within a network.The bottom-line is, though, that you now have three levels of architecture; the installation itself (the root), the individual networks and the individual sites within those networks. How you arrange them is ultimately almost entirely up to you.
13. So, we’ve already established that it slices, it dices and juliennes fries; but that’s not all.There are a handful of methods you can use to enhance the way your WordPress Multi-Network installation works. For instance, if you want to limit the amount of control individual Super Admins have over their own networks, you can use the Extended Super Admins plugin (shameless plug).I’ve also developed a series of plugins that give you the ability to handle some tasks on a multi-network basis, rather than having to perform those tasks on a network-by-network basis. Together, these plugins enable you to:Make a user a Super Admin for all networksNetwork-activate/Network-deactivate a plugin on all networksNetwork-enable/Network-disable a theme on all networksStore some information in a global table for use on all networks (requires a plugin to be compatible – only my plugins are as of yet – or for you to make modifications yourself)
14. It’s not all sunshine, lollipops and rainbows, though. There are some disadvantages to running WordPress in a multi-network set up.First of all, you’re adding a new level of uncertainty when it comes to the compatibility of different add-ons. Most plugins, when installed and network-activated, will only store and use their settings on that individual network. Even when you use my functions to multi-network activate a plugin, unless that plugin is specifically compatible with multi-network, those settings won’t carry over from one network to another. However, there are a handful of plugin that, for whatever reason, will use the settings you configure on the root network for all networks in the multi-network installation (WPTouch Pro is one of those).Also, as with WordPress Multisite, there are some plugins that can’t even be network-activated. Obviously, if a plugin can’t be network-activated, it can’t be multi-network-activated, either. Instead, you’ll have to activate and configure that plugin on each individual site.There are also potential conflicts when it comes to multi-network. For instance, I have no idea how, or even if, either of the wildly popular caching plugins will work. W3 Total Cache cannot be network-activated, so it will most likely work properly in multi-network, but has to be configured on a site-by-site basis. WP Super Cache can be network-activated. However, because of the way it works, it will affect the entire installation even if it’s not configured on the entire installation (i.e., you can’t turn it off for individual sites or networks).There can also be serious issues with plugins and themes that are coded poorly. Back in the days of WPMU, there were quite a few plugins that incorrectly relied on the idea that your “site” (or “network” as it’s known in WordPress now) would always have an ID of 1.Finally, when it comes to mu-plugins, you have to understand that they will be active everywhere. There is no “mu-plugins” folder for each individual network in a multi-network installation.
15. When it comes to using WordPress Multi-Network, remember the adage “with great power comes great responsibility.”Basically, it boils down to the idea that multi-network can add a lot of new functionality and options to your WordPress installation, but it’s not something to be taken lightly. You will need to be even more diligent about the plugins and themes you make available, and you’ll need to pay even closer attention to the way things are set up.Not all things will work the way you expect them to, and, just when you figure out how things normally work, something will come along that does just the opposite.