Orders the pages with children under parents in a flat list.

It uses auxiliary structure to hold parent-children relationships and runs in O(N) complexity

$pages WP_Post[] Required

Posts array (passed by reference).

$page_id int Optional

Parent page ID. Default 0.

string[] Array of post names keyed by ID and arranged by hierarchy. Children immediately follow their parents.

File: wp-includes/post.php. View all references

function get_page_hierarchy( &$pages, $page_id = 0 ) {
	if ( empty( $pages ) ) {
		return array();
	}

	$children = array();
	foreach ( (array) $pages as $p ) {
		$parent_id                = (int) $p->post_parent;
		$children[ $parent_id ][] = $p;
	}

	$result = array();
	_page_traverse_name( $page_id, $children, $result );

	return $result;
}