Question

Can anyone describe the pseudocode for how WordPress handles its upgrades? As in, you go into WordPress admin and choose to upgrade the version of WordPress.

I mean, does it use FTP APIs locally? Does it send credentials to another host which reconnects back with FTP APIs? Does it download files with Curl? Does it polyfill if a given API isn’t there and go another route? Does it test file permissions to see which API to use?

I’ve got a client who wants something like this built into a web application unrelated to WordPress.

Answer 1

Have a look it wp-admin/includes/update.php and wp-admin/includes/class-wp-upgrader.php

And here for some explanation: http://tech.ipstenu.org/2011/how-the-wordpress-upgrade-works/