standards – Knowboard

Theme Development Standards

WordPress Themes should be coded using the following standards:

Use well-structured, error-free PHP and valid HTML. See WordPress Coding Standards.
Use clean, valid CSS. See CSS Coding Standards.
Follow design guidelines in Site Design and Layout.

A theme can optionally use a functions file, which resides in the theme subdirectory and is named functions.php. This file basically acts like a plugin, and if it is present in the theme you are using, it is automatically loaded during WordPress initialization (both for admin pages and external pages). Suggested uses for this file: