[kayodelycaon]

The difference is SSI is extremely fast and quite limited. You’re not supposed to write your entire website in it.

[mweberxyz]

I'd be interested in seeing what the performance difference between the NGINX SSI and <?php echo $_ENV['SIGN_OUT_URL'] ?> is. Just because PHP _can_ be slow, doesn't mean it _must_ be slow.

[oarsinsync]

Also SSIs predate PHP by some time