 Thank you. That was kind Hello, welcome to multi-site who here has worked with multi-site before Everybody so I don't need to be here Who's a beginning developer or thinks of themselves as a beginning developer an advanced developer or been doing this for a while Okay, well Hopefully this should help everybody a little bit. I think the thing I want you to take away from this is How the internals of multi-site work because I think an awareness of that can help you as you're doing things with multi-site So we're gonna start with a little history Because I think well the history of multi-site dates all the way back to before WordPress So having that as a context for What we're working with can sometimes help it definitely helps when you're trying to figure out why different decisions were made in Multi-site code that we then either use or have to work around So back in 2003 when Matt and Mike forked B2 into WordPress There were two other forks at the time B2 evolution and B2 plus plus B2 plus plus is a fork created by Donna co-equive That's he used to install B2 for many different users as part of his Linux users forums blogs that Linux that I eat So pretty much the same exact thing where one installation of B2 would power many different sites When the first version of WordPress was released the Matt reached out to Donica and asked him if he'd like to be a Core developer with WordPress and asked if we could merge the two projects together Donica said yes And B2 plus plus became WordPress MU So for a few years WordPress MU development kind of existed here while WordPress was here And then every time a new WordPress release came out it would be merged into MU and at some time and be distributed in 2005 WordPress comm started Matt hired Donica as the first automatic employee. I believe and Then WordPress multi-site kind of really got started the community grew around multi-site WordPress comm of course being an open-blog registration For many different users many different sites And then in 2009 Matt announced at the state of the word that multi-site was going to be merged into WordPress proper 2010 there's a huge effort if you ever have hours ticket one one six four four Is a long ticket to read through on the merge of multi-site? So that's how we got here And now we can get into details So we're gonna walk through four things they all kind of relate pretty closely The structure of multi-site itself and the bootstrap process that kind of helps determine what part of that structure we're using Plugins and themes how those are loaded the context of your code and how it's important to be aware What part of multi-site you're in as you work and then finally a few common solutions to questions that get asked often by People who are using multi-site for the first time So WordPress itself is I think of it as a router of requests So a request comes in WordPress routes it to wherever it needs to go a Single post a post archive Category archive, you know something so it follows this common pattern that a lot of different PHP applications use where it's index dot PHP Kind of controls where things are gonna go. So we have a bunch of logic that determines, you know, I receive a request Where does it go? So WordPress multi-site works the same way But it uses tables to to also separate these requests When you install WordPress for the first time you get a set of 10 tables You get posts options comments terms users The second you install WordPress multi-site The users table become global and then you get a set of another six tables That hold the sites the networks and then some registration and sign-up information Now at this point you have a multi-site It only has one site, but it can be considered a network