Briany from Ireland has a cool idea (put the guilt away, Briany, I think this is a pretty wild concept and I like it). This is the sort of ‘support’ email I love because it’s not a yes/no answer, but a theoretical concept to think about and parse!
Here’s the meat of the email:
SO MY FASCINATING QUESTION IS THIS; In a multi site network is there any way to use 2 separate themes for each or any sub-site based on the URL used (or any other method) Example 1 Visit www.sitename.platform.com and view the whole site using theme A (Standard) Visit www.sitename.com and view the whole site using theme B (custom)
At first I thought “Briany can’t possibly be asking ‘How do I activate a separate theme per site.’” and then I realized the question was for the network! So to phrase it in WordPress terms, if I visit the site via foo.example.com, I get theme foo on every site on the network.
(If you just want Site A to have one theme, and Site B another, that’s easy. Either network activate the theme and select it on the site, or go to WP Admin -> Network -> Sites, click on edit, click on the themes tab, and activate the theme you want for the sites. Then go back to the site and select that theme. A couple steps, yes, but relatively easy.)
Theoretically yes, yes you can. There’s a plugin called Theme Switcher which lets users pick, and based on some code on StackExchange, you can change the theme based on users, but the issue here is that you want to only change it per domain for that user.
It’s certainly possible to change settings by detecting the domain, I do that with SSL.
if ( $_SERVER["HTTP_HOST"] == "foo.example.com" ) {
// My Code Here
}
That’s the easy part. The hard part is keeping that setting when I go from foo.example.com to example.com…
I sat and kicked this idea around for a while. It would be much easier on a single install of WordPress, since I could make everything relative and then just use the host name. But you have to have a way to track the starter domain, and have it be per-visitor, which means you have to use cookies, and read from that, using setcookie() (which is a PHP thing, not WP specific).
At that point, I think I would close the book and say “No, it’s possible, but not a good idea.”
Why, you ask? Caching. How the hairy hell could I possibly cache that if the theme changes every time for every user? Maybe, maybe, I would do it with multi-networks, and define a theme per network, but not per-domain. Obviating any caching would pretty much kill my sites, and even a good opcode cache (I use memcache) will be usless in that scenario.
By the way, there are a lot of neato plugins to change themes based on weird things, like Domain Theme, which is great for single installs of WordPress.
