Anatomy of a Theme: header.php, footer.php and sidebar.php

In WordPress, themes are modular. The files header.php, footer.php, and sidebar.php form the basic structure of a page layout. Together, they help break up the page into reusable components.

Anatomy of a Theme

Common Template Parts:

File	Purpose
`header.php`	Top section: metadata, site title, logo, navigation, etc.
`footer.php`	Bottom section: copyright, footer nav, scripts, etc.
`sidebar.php`	Sidebar: widgets, categories, search, recent posts, etc.

1. `header.php`

Purpose: Contains everything from the top of the page to the start of content—like <!DOCTYPE>, <head>, logo, menu.

Example:

<!DOCTYPE html>
<html <?php language_attributes(); ?>>
<head>
  <meta charset="<?php bloginfo('charset'); ?>">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title><?php bloginfo('name'); ?></title>
  <?php wp_head(); ?>
</head>
<body <?php body_class(); ?>>
  <header>
    <h1><a href="<?php echo home_url(); ?>"><?php bloginfo('name'); ?></a></h1>
    <p><?php bloginfo('description'); ?></p>
    <nav>
      <?php wp_nav_menu(['theme_location' => 'main-menu']); ?>
    </nav>
  </header>

In your main template (index.php, page.php, etc.), load it with:

<?php get_header(); ?>

2. `footer.php`

Purpose: Bottom part of the page. Contains closing tags, footer widgets, and wp_footer() (important for plugins and scripts).

Example:

 <footer>
    <p>&copy; <?php echo date('Y'); ?> <?php bloginfo('name'); ?>. All rights reserved.</p>
  </footer>
  <?php wp_footer(); ?>
</body>
</html>

Include it in templates using:

<?php get_footer(); ?>

3. `sidebar.php`

Purpose: Optional side panel, usually used for widgets, search, recent posts, etc.

Example:

<aside id="sidebar" class="widget-area">
  <?php if ( is_active_sidebar( 'main-sidebar' ) ) : ?>
    <?php dynamic_sidebar( 'main-sidebar' ); ?>
  <?php else : ?>
    <p>Add widgets via Appearance > Widgets.</p>
  <?php endif; ?>
</aside>

✅ Register Sidebar in functions.php:

function mytheme_widgets_init() {
  register_sidebar([
    'name' => 'Main Sidebar',
    'id' => 'main-sidebar',
    'before_widget' => '<section class="widget">',
    'after_widget'  => '</section>',
    'before_title'  => '<h2 class="widget-title">',
    'after_title'   => '</h2>',
  ]);
}
add_action('widgets_init', 'mytheme_widgets_init');

Add in templates using:

<?php get_sidebar(); ?>

Summary Diagram

[ header.php ]
    ↑
[ index.php / page.php / single.php ]
    ↓
[ sidebar.php ]        [ footer.php ]

Breaking

Anatomy of a Theme: header.php, footer.php and sidebar.php