Browsers may cache 302 redirect to install.php

[smerriman]

• Upload the Wordpress files and fill in the wp-config.php information
• Visit the Wordpress URL in your browser; you are redirected to /wp-admin/install.php
• Proceed with the installation
• Visit the Wordpress URL in your browser.

Firefox, at least, caches the 302 redirect and keeps sending you to /wp-admin/install.php, acting as if you haven't installed Wordpress at all. Restarting Firefox clears the 302 cache, after which it works perfectly.

I'm not sure what the best solution is - ideally it should be redirected in a way that doesn't cache the result, if possible - but at the very least, the installation page shouldn't be acting as if Wordpress isn't installed and asking you for installation details.

[SergeyBiryukov]

Replying to smerriman:

but at the very least, the installation page shouldn't be acting as if Wordpress isn't installed and asking you for installation details.

We already detect that: tags/3.9.2/src/wp-admin/install.php#L142​.

[smerriman]

Hm, I see. Every time I'm redirected to /wp-admin/install.php, I'm seeing the original installation page and form; only when I do a hard refresh of that page does it change to the 'Wordpress is already installed' message. So it's caching both the redirect, and the install.php output.

[SergeyBiryukov]

I think adding nocache_headers()​ to wp_not_installed()​ should resolve this.

Related: #21745.

[johnbillion]

This makes sense. We send no-cache headers on the login screen, database upgrade screens, and on the rest of the admin area.

[SergeyBiryukov]

wp_not_installed() is called unconditionally​, so 29248.patch​ doesn't work as expected.

See 29248.2.patch​.

[nacin]

Fine.

[SergeyBiryukov]

In 29599:

Send nocache_headers() on installation screens and when redirecting to them.

fixes #29248.