get_page_children() │ WP 1.5.1

Collects child pages from the provided array of pages. All levels of nesting are processed.

The function works as a filter and does not make any database queries. It filters the array from the second parameter: finds all child pages for the specified $page_id. All levels of nesting are taken into account during filtering.

No Hooks.

Returns

WP_Post[]. Array of WP_Post objects.

Usage

get_page_children( $page_id, $pages );
$page_id(integer) (required)
ID of the page for which child pages need to be retrieved.
$pages(array) (required)
List of post objects to search for child pages.

Examples

0

#1 Leave only the children to Portfolio page 

// Get all the pages to be searched.
$all_pages = ( new WP_Query() )->query( [ 
	'post_type' => 'page', 
	'posts_per_page' => -1 
] );

// the page whose children you want to get
$about_id = 7;

// let's leave only the children to Portfolio
$about_childrens = get_page_children( $about_id, $all_pages );

// let's simplify the output
foreach( $about_childrens as & $page ){
	unset( 
		$page->post_content, 
		$page->post_date_gmt, 
		$page->post_password, 
		$page->post_modified_gmt, 
		$page->post_content_filtered, 
		$page->post_mime_type
	);
}

//result
print_r( $about_childrens );

We get it:

Array
(
	[0] => WP_Post Object
		(
			[ID] => 10124
			[post_author] => 12
			[post_date] => 2018-05-19 08:11:19
			[post_title] => Privacy Policy
			[post_excerpt] => 
			[post_status] => publish
			[comment_status] => closed
			[ping_status] => closed
			[post_name] => privacy-policy
			[to_ping] => 
			[pinged] => 
			[post_modified] => 2018-09-12 05:28:35
			[post_parent] => 7
			[guid] => /about/privacy-policy
			[menu_order] => 3
			[post_type] => page
			[comment_count] => 0
			[filter] => raw
		)

	[1] => WP_Post Object
		(
			[ID] => 9976
			[post_author] => 12
			[post_date] => 2018-05-05 01:01:09
			[post_title] => Active users
			[post_excerpt] => 
			[post_status] => publish
			[comment_status] => closed
			[ping_status] => open
			[post_name] => best-users
			[to_ping] => 
			[pinged] => 
			[post_modified] => 2018-05-05 02:04:25
			[post_parent] => 7
			[guid] => /about/best-users
			[menu_order] => 2
			[post_type] => page
			[comment_count] => 0
			[filter] => raw
		)

	[2] => WP_Post Object( ... )

	[3] => WP_Post Object( ... )

)
0

#2 Leave only the children posts (for the CPT)

Let's get all posts of locations CPT and leave only children of post 12:

$location_parent_id = 12;

// Instead of calling and passing query parameter differently, we're doing it exclusively
$all_locations = get_pages( [ 
	'post_type'   => 'locations',
	'post_status' => array( 'publish', 'pending' ) // my custom choice
] );

// Using the function
$inherited_locations = get_page_children( $location_parent_id, $all_locations );

// echo what we get back from WP to the browser
echo '' . print_r( $inherited_locations, true ) . '';

Changelog

Since 1.5.1 Introduced.

get_page_children() code WP 6.8.3

wp-includes/post.php 
function get_page_children( $page_id, $pages ) {
	// Build a hash of ID -> children.
	$children = array();
	foreach ( (array) $pages as $page ) {
		$children[ (int) $page->post_parent ][] = $page;
	}

	$page_list = array();

	// Start the search by looking at immediate children.
	if ( isset( $children[ $page_id ] ) ) {
		// Always start at the end of the stack in order to preserve original `$pages` order.
		$to_look = array_reverse( $children[ $page_id ] );

		while ( $to_look ) {
			$p           = array_pop( $to_look );
			$page_list[] = $p;
			if ( isset( $children[ $p->ID ] ) ) {
				foreach ( array_reverse( $children[ $p->ID ] ) as $child ) {
					// Append to the `$to_look` stack to descend the tree.
					$to_look[] = $child;
				}
			}
		}
	}

	return $page_list;
}

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