How do register_sidebar() and get_sidebar() work together?

Question

Disclaimer: I am brand spanking new to WP.

I am using the Starkers HTML5 framework theme. In the functions.php I see this code:

function starkers_widgets_init() {

  // Area 1, located at the top of the sidebar.
  register_sidebar( array(
    'name' => __( 'Primary Widget Area', 'starkers' ),
    'id' => 'primary-widget-area',
    'description' => __( 'The primary widget area', 'starkers' ),
    'before_widget' => '<li>',
    'after_widget' => '</li>',
    'before_title' => '<h3>',
    'after_title' => '</h3>',
  ) );

  // Area 3, located in the footer. Empty by default.
  register_sidebar( array(
    'name' => __( 'First Footer Widget Area', 'starkers' ),
    'id' => 'first-footer-widget-area',
    'description' => __( 'The first footer widget area', 'starkers' ),
    'before_widget' => '<li>',
    'after_widget' => '</li>',
    'before_title' => '<h3>',
    'after_title' => '</h3>',
  ) );

  // ... more calls to register_sidebar() ... 
}

And in footer.php I see this code:

<?php get_sidebar( 'footer' ); ?>

I don't understand how get_sidebar() knows how to take that string argument and find the appropriate widgets that were defined by register_sidebar(). In the functions.php snippet I posted above. There isn't any mention of "footer" except for the name, id and description properties. But it would seem odd to me that get_sidebar() would search for 'footer' inside those properties.

Does this make sense what I am asking? Is there some missing piece?

The reasons I am asking is because - I would like to know more about the WP architecture - I would like to be able to define a custom widget area and know how to render it on a specific page.

Thanks a ton.

Answer 1

You just call get_sidebar() from index.php and it loads the theme file sidebar.php.

register_sidebar(), on the other hand, is used for widgets where plugins and such want to dynamically add content in your sidebar.php file if your theme supports it.

In your case, is there a file called sidebar-footer.php in your theme's directory?

Answer 2

get_sidebar('footer') attempts to load sidebar-footer.php from the active theme. Starkers does provide this file. Check starkers/sidebar-footer.php and things should become clear.

Answer 3

I've never bothered with get_sidebar(). Instead I just use dynamic_sidebar(). You'd call it like this:

dynamic_sidebar('first-footer-widget-area');

And that takes care of the whole sidebar. No more file inclusions, no more cluttered theme folders. If I want to have 5 different sidebars, it doesn't add any files, only extra functions in functions.php.