register_sidebar( array|string $args = array() ): string

Description

Compatibility

Present in every tracked release (6.7.7 to 7.1.0), and compiles on PHP 7.4 through 8.6-dev.

Parameters

$argsarray|stringoptional

Array or string of arguments for the sidebar being registered.Default: array()

• $namestringdefault: 'Sidebar $instance'

  The name or title of the sidebar displayed in the Widgets interface.

• $idstringdefault: 'sidebar-$instance'

  The unique identifier by which the sidebar will be called.

• $descriptionstringdefault: empty string

  Description of the sidebar, displayed in the Widgets interface.

• $classstringdefault: empty

  Extra CSS class to assign to the sidebar in the Widgets interface.

• $before_widgetstringdefault: is an opening list item element

  HTML content to prepend to each widget's HTML output when assigned to this sidebar. Receives the widget's ID attribute as %1$s and class name as %2$s.

• $after_widgetstringdefault: is a closing list item element

  HTML content to append to each widget's HTML output when assigned to this sidebar.

• $before_titlestringdefault: is an opening h2 element

  HTML content to prepend to the sidebar title when displayed.

• $after_titlestringdefault: is a closing h2 element

  HTML content to append to the sidebar title when displayed.

• $before_sidebarstringdefault: empty string

  HTML content to prepend to the sidebar when displayed. Receives the $id argument as %1$s and $class as %2$s. Outputs after the 'dynamic_sidebar_before' action.

• $after_sidebarstringdefault: empty string

  HTML content to append to the sidebar when displayed. Outputs before the 'dynamic_sidebar_after' action.

• $show_in_restbool

  Whether to show this sidebar publicly in the REST API. Defaults to only showing the sidebar to administrator users.

Return value

string

Sidebar ID added to $wp_registered_sidebars global.

Performance profile

How much work a call to register_sidebar() does, and what it touches: the algorithmic scaling, the Zend instruction count per call across PHP versions, the hooks it hands control to, and the core code that calls it. Measured from the compiled opcodes, not a stopwatch, so every number is identical on any machine running the same PHP version, and every function in core is ranked by cost.

Cost class

Trivial

Touches nothing outside its own arguments.

Scaling

Constant

No loop in the body: the same number of instructions runs whatever you pass in.

Instructions

47–63

Executed per call on PHP 8.5, depending on the branch taken. The body compiles to 63.

Plugin surface

2 hooks

Third-party callbacks on 'register_sidebar_defaults', 'register_sidebar' run inside this call, and their cost is not bounded by anything here.

Called by

12

12 places in core call this, so the cost is paid more often than your own code shows.

What it touches

• hookthird-party callbacksapply_filters()called directly

Further down the call graph this can also reach query, option, cache, serialize and transient. Those are the worst case, several calls deep and usually down an error path, not what a normal call pays.

What one call costs · 2 distinct outcomes

One number would be a lie: the work depends on which branch runs. These are every distinct cost register_sidebar() can have, taken from its control-flow graph on PHP 8.5.

Hooks and filters fired · 2

2 hooks fire while register_sidebar() runs, in this order:

1. 1
   apply_filters( register_sidebar_defaults )filterline 300 (+31 into the body)

   Filters the sidebar default arguments.

2. 2
   do_action( register_sidebar )actionline 327 (+58 into the body)

   Fires once a sidebar has been registered.

Uses · 6

• __()Retrieves the translation of $text.
• wp_parse_args()Merges user defined arguments into defaults array.
• apply_filters()Calls the callback functions that have been added to a filter hook.
• _doing_it_wrong()Marks something as being incorrectly called.
• add_theme_support()Registers theme support for a given feature.
• do_action()Calls the callback functions that have been added to an action hook.

Used by · 12

• register_sidebars()Creates multiple sidebars.
• twenty_twenty_one_widgets_init()Registers widget area.
• twentyeleven_widgets_init()Registers sidebars and widgetized areas.
• twentyfifteen_widgets_init()Registers widget area.
• twentyfourteen_widgets_init()Registers three Twenty Fourteen widget areas.
• twentynineteen_widgets_init()Registers widget area.
• twentyseventeen_widgets_init()Registers widget area.
• twentysixteen_widgets_init()Registers a widget area.
• twentyten_widgets_init()Registers widgetized areas, including two sidebars and four widget-ready columns in the footer.
• twentythirteen_widgets_init()Registers two widget areas.
• twentytwelve_widgets_init()Registers sidebars.
• twentytwenty_sidebar_registration()Registers widget areas.

Source code

View on Trac ↗View on GitHub ↗

269function register_sidebar( $args = array() ) {270	global $wp_registered_sidebars;271 272	$i = count( $wp_registered_sidebars ) + 1;273 274	$id_is_empty = empty( $args['id'] );275 276	$defaults = array(277		/* translators: %d: Sidebar number. */278		'name'           => sprintf( __( 'Sidebar %d' ), $i ),279		'id'             => "sidebar-$i",280		'description'    => '',281		'class'          => '',282		'before_widget'  => '<li id="%1$s" class="widget %2$s">',283		'after_widget'   => "</li>\n",284		'before_title'   => '<h2 class="widgettitle">',285		'after_title'    => "</h2>\n",286		'before_sidebar' => '',287		'after_sidebar'  => '',288		'show_in_rest'   => false,289	);290 291	/**292	 * Filters the sidebar default arguments.293	 *294	 * @since 5.3.0295	 *296	 * @see register_sidebar()297	 *298	 * @param array $defaults The default sidebar arguments.299	 */300	$sidebar = wp_parse_args( $args, apply_filters( 'register_sidebar_defaults', $defaults ) );301 302	if ( $id_is_empty ) {303		_doing_it_wrong(304			__FUNCTION__,305			sprintf(306				/* translators: 1: The 'id' argument, 2: Sidebar name, 3: Recommended 'id' value. */307				__( 'No %1$s was set in the arguments array for the "%2$s" sidebar. Defaulting to "%3$s". Manually set the %1$s to "%3$s" to silence this notice and keep existing sidebar content.' ),308				'<code>id</code>',309				$sidebar['name'],310				$sidebar['id']311			),312			'4.2.0'313		);314	}315 316	$wp_registered_sidebars[ $sidebar['id'] ] = $sidebar;317 318	add_theme_support( 'widgets' );319 320	/**321	 * Fires once a sidebar has been registered.322	 *323	 * @since 3.0.0324	 *325	 * @param array $sidebar Parsed arguments for the registered sidebar.326	 */327	do_action( 'register_sidebar', $sidebar );328 329	return $sidebar['id'];330}

Changelog

Introduced in 2.2.0. Unchanged from 6.7.7 through 7.1.0.

1. 6.7.7
2. 6.8.8
3. 6.9.7
4. 7.0.4
5. 7.1.0

Signature, return type and hooks compared across 5 parsed releases.

About this page

Parsed data

Generated from the wordpress-develop 7.1.0 tag, from src/wp-includes/widgets.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.

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