> This lets you do things like have the main page be the pre-page content and the included HTML be a heavily cached site-wide shell, and then another per-user include with personalized HTML - all cached appropriately.
If you can do your includes at page load time, you've been able to do this for 25 years with xslt; it's been built into the browser almost since the beginning of the web!
I've played around with doing exactly that: include a `/myinfo.xml` document that has information about your user, and then the rest of the page template just grabs `$myinfo/user/@name` or whatever wherever it needs. The neat thing is it has graceful degradation by default: if the request fails, then your include will be empty and you can treat it as a logged out page. So you can e.g. display the username and logout button in the top right if logged in, or a login button if not. You can also e.g. include a CSRF token in your info document and plop that into any forms in your page by just doing `value="{$myinfo/csrf-token}"` or whatever.
If you can do your includes at page load time, you've been able to do this for 25 years with xslt; it's been built into the browser almost since the beginning of the web!
I've played around with doing exactly that: include a `/myinfo.xml` document that has information about your user, and then the rest of the page template just grabs `$myinfo/user/@name` or whatever wherever it needs. The neat thing is it has graceful degradation by default: if the request fails, then your include will be empty and you can treat it as a logged out page. So you can e.g. display the username and logout button in the top right if logged in, or a login button if not. You can also e.g. include a CSRF token in your info document and plop that into any forms in your page by just doing `value="{$myinfo/csrf-token}"` or whatever.