Retrieving page list HTML in WordPress using walk_page_tree

The walk_page_tree function in WordPress is a part of the Walker class that is used to generate a nested, hierarchical list of pages. Specifically, it outputs the pages in a nested unordered list (<ul>), where each page is an individual list item (<li>).

This function is primarily used when building navigation menus, as it allows the creation of hierarchical menus that accurately reflect the structure of the site. It is also useful in situations where you need to display a list of pages in a hierarchical format, such as in a sidebar widget or a dropdown menu.

While the walk_page_tree function is capable of generating a nested list of pages, it does not automatically include any links to the pages. This means that if you want to make the pages clickable, you will need to manually add the appropriate <a> tags within the <li> tags.

It’s important to note that the walk_page_tree function only outputs the pages in a hierarchical format. It does not sort the pages in any particular order. If you need the pages to be sorted in a specific order, you will need to do this manually before calling the walk_page_tree function.

Parameters Accepted by walk_page_tree Function

The walk_page_tree function in WordPress accepts four required parameters. These parameters are as follows:

  • $pages (array) – This is a required parameter.
  • $depth (int) – This is also a required parameter.
  • $current_page (int) – This parameter is required as well.
  • $args (array) – This is the final required parameter.

Return Value of walk_page_tree Function

The walk_page_tree function returns a string value. The return value is a string that represents the outcome of the function’s operation.

Examples

How to Display a List of Pages Using walk_page_tree Function

The following code snippet displays a list of pages using the walk_page_tree function:

$pages = get_pages(); 
$depth = 0; 
$current_page = 0; 
$args = array(
 'title_li' => __('Pages'),
 'sort_column' => 'menu_order, post_title',
);
echo walk_page_tree( $pages, $depth, $current_page, $args );

This code snippet first retrieves all pages using the get_pages function. It then sets the $depth and $current_page to 0, which means it will display all pages and not just the children of a specific page. The $args array is used to set the title of the list to “Pages” and to sort the pages by menu order and title. Finally, it displays the list of pages using the walk_page_tree function.

How to Display a List of Child Pages Using walk_page_tree Function

The following code snippet displays a list of child pages of a specific page using the walk_page_tree function:

$pages = get_pages('child_of=10'); 
$depth = 0; 
$current_page = 10; 
$args = array(
 'title_li' => __('Child Pages'),
 'sort_column' => 'menu_order, post_title',
);
echo walk_page_tree( $pages, $depth, $current_page, $args );

This code snippet first retrieves all child pages of the page with ID 10 using the get_pages function. It then sets the $current_page to 10, which means it will display all child pages of this page. The $args array is used to set the title of the list to “Child Pages” and to sort the pages by menu order and title. Finally, it displays the list of child pages using the walk_page_tree function.

How to Display a List of Pages in a Specific Depth Using walk_page_tree Function

The following code snippet displays a list of pages in a specific depth using the walk_page_tree function:

$pages = get_pages(); 
$depth = 2; 
$current_page = 0; 
$args = array(
 'title_li' => __('Pages'),
 'sort_column' => 'menu_order, post_title',
);
echo walk_page_tree( $pages, $depth, $current_page, $args );

This code snippet first retrieves all pages using the get_pages function. It then sets the $depth to 2, which means it will display all pages in a depth of 2. The $args array is used to set the title of the list to “Pages” and to sort the pages by menu order and title. Finally, it displays the list of pages using the walk_page_tree function.

Conclusion

The walk_page_tree function in WordPress is a versatile tool that plays a critical role in the generation of nested page lists. This function is particularly beneficial when working with hierarchical post types or when you need to generate a structured list of pages. It achieves this by walking through the page tree and applying a specified walker class to generate the required output. This functionality can be leveraged in a variety of scenarios, such as creating custom navigation menus, generating sitemaps, or displaying a structured list of child pages under a parent page.

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