# Classic Theme Sidebars Widgets
> Build or audit classic theme widget areas and sidebars for WP 7.1. Covers `widgets_init`, `register_sidebar()`, stable sidebar IDs, `before_widget` and `before_title` wrappers, `dynamic_sidebar()`, `is_active_sidebar()`, `get_sidebar()`, `sidebar-{name}.php`, `show_in_rest`, semantic aside/footer/header widget areas, block-widget era compatibility, and common mistakes such as missing IDs, changing IDs after release, hardcoded widgets, bad wrapper placeholders, and rendering empty sidebars.
- Skill: `lonsdale201/classic-theme-sidebars-widgets` (Agent Skill)
- Install (CLI): `npx skillmds@latest add lonsdale201/classic-theme-sidebars-widgets`
- Raw SKILL.md: https://api.skillmd.com/api/skills/lonsdale201/classic-theme-sidebars-widgets/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Security
- Author: Lonsdale201 (https://skillmd.com/u/lonsdale201)
- Updated: 2026-09-10
- Page: https://skillmd.com/skills/lonsdale201/classic-theme-sidebars-widgets
---
# Classic Theme Sidebars and Widgets
Use this when adding or reviewing widget areas in a classic PHP theme: blog sidebars, footer columns, header widget areas, shop sidebars, or template-specific widget regions.
In WordPress naming, "sidebar" means a registered widget area. It does not have to appear visually at the side of the layout.
## When to Use This Skill
- Registering widget areas with `register_sidebar()`.
- Creating `sidebar.php` or `sidebar-{name}.php`.
- Rendering `dynamic_sidebar()`.
- Checking empty widget area behavior.
- Migrating hardcoded footer/header content to user-manageable widget areas.
- Reviewing widget markup semantics and REST exposure.
## Register Widget Areas
Register widget areas on `widgets_init`.
```php
add_action( 'widgets_init', 'mytheme_register_sidebars' );
function mytheme_register_sidebars() {
register_sidebar(
array(
'name' => __( 'Primary sidebar', 'textdomain' ),
'id' => 'sidebar-1',
'description' => __( 'Widgets shown beside the main content.', 'textdomain' ),
'before_widget' => '',
'before_title' => '',
'show_in_rest' => false,
)
);
}
```
Rules:
- Always provide an explicit `id`.
- Treat IDs as persistent storage keys. Changing an ID after release can orphan assigned widgets.
- Keep `%1$s` and `%2$s` in `before_widget`; core substitutes widget ID and classes.
- Choose semantic wrappers: `aside` for side content, `section` for content regions, `div` only when no semantic element fits.
- Use translated `name` and `description`.
- `register_sidebar()` adds theme support for widgets.
## Multiple Areas
Use predictable IDs for repeated footer columns.
```php
for ( $i = 1; $i <= 4; $i++ ) {
register_sidebar(
array(
'name' => sprintf(
/* translators: %d: Footer column number. */
__( 'Footer column %d', 'textdomain' ),
$i
),
'id' => 'footer-' . $i,
'before_widget' => '',
'before_title' => '',
)
);
}
```
Rules:
- Keep generated IDs stable.
- Use translator comments for numbered names.
- Do not let Customizer options or request values create arbitrary sidebar IDs.
## Render a Sidebar
Use `is_active_sidebar()` before outputting layout wrappers.
```php
if ( is_active_sidebar( 'sidebar-1' ) ) :
?>
false` unless the widget area must be exposed publicly through REST.
- If enabling REST exposure, assume the sidebar structure is public data.
- Classic themes can still render widget areas with `dynamic_sidebar()` even when the admin widget UI uses block widgets.
- Do not disable block widgets just because the theme is classic unless the project has a tested compatibility reason.
## Markup and Accessibility
Good widget-area output:
- Uses a landmark or labeled region when it is a major page area.
- Does not create many unlabeled `aside` landmarks.
- Keeps heading levels sensible for the template context.
- Lets individual widgets output their own content.
Wrapper choice examples:
| Area | Wrapper |
|---|---|
| Blog sidebar | `