By moving from `.html` to `.php` files, we can prevent directory listings, and ensure that WordPress can load.
Fixes#52299.
Props lucasbustamante, xkon, freewebmentor, SergeyBiryukov, whyisjake.
git-svn-id: https://develop.svn.wordpress.org/trunk@50037 602fd350-edb4-49c9-b593-d223f7449a82
This brings consistency to this often-used method, and allows IDEs to provide help to developers when using its `$factory` parameter.
See #51344
git-svn-id: https://develop.svn.wordpress.org/trunk@49603 602fd350-edb4-49c9-b593-d223f7449a82