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get_post_ancestors()

get_post_ancestors( int|WP_Post $post ): int[]

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Retrieves the IDs of the ancestors of a post.

Parameters

$postint|WP_Postrequired
Post ID or post object.

Return

int[] Array of ancestor IDs or empty array if there are none.

Source

 * @return int[] Array of ancestor IDs or empty array if there are none.
 */
function get_post_ancestors( $post ) {
	$post = get_post( $post );

	if ( ! $post || empty( $post->post_parent ) || $post->post_parent === $post->ID ) {
		return array();
	}

	$ancestors = array();

	$id          = $post->post_parent;
	$ancestors[] = $id;

	while ( $ancestor = get_post( $id ) ) {
		// Loop detection: If the ancestor has been seen before, break.
		if ( empty( $ancestor->post_parent ) || $ancestor->post_parent === $post->ID
			|| in_array( $ancestor->post_parent, $ancestors, true )
		) {
			break;
		}

		$id          = $ancestor->post_parent;
		$ancestors[] = $id;

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Changelog

VersionDescription
2.5.0Introduced.

User Contributed Notes

  1. Skip to note 5 content
    Codex
    You must log in to vote on the helpfulness of this noteVote results for this note: 1You must log in to vote on the helpfulness of this note

    Get Ancestors Page Thumbnail
    Get the top level page thumbnail and display it!

    <?php
global $post;
$parents = get_post_ancestors( $post );
$id = $post->ID;
/* Get the ID of the 'top most' Page */
if ( ! empty( $parents ) ) {
    $id = array_pop( $parents );
}
if ( has_post_thumbnail( $id ) ) {
    echo get_the_post_thumbnail( $id, 'thumbnail' );
}
?>
  2. Skip to note 6 content
    Codex
    You must log in to vote on the helpfulness of this noteVote results for this note: 0You must log in to vote on the helpfulness of this note

    Get Ancestors Page Slug
    This example returns the highest page {slug} in a tree and uses it as a Body_Class, so the parent and all children will have the same Body Class!

    This example for a twenty eleven child theme in the header.php file

    </head>

<?php
/* Get the Page Slug to Use as a Body Class, this will only return a value on pages! */
$class = '';
/* is it a page */
if( is_page() ) { 
	global $post;
	/* Get an array of Ancestors and Parents if they exist */
	$parents = get_post_ancestors( $post->ID );
	/* Get the top Level page->ID count base 1, array base 0 so -1 */ 
	$id = ($parents) ? $parents[count($parents)-1]: $post->ID;
	/* Get the parent and set the $class with the page slug (post_name) */
	$parent = get_post( $id );
	$class = $parent->post_name;
}
?>

<body <?php body_class( $class ); ?>>
  3. Skip to note 7 content
    Codex
    You must log in to vote on the helpfulness of this noteVote results for this note: 0You must log in to vote on the helpfulness of this note

    Get Ancestors Post Meta
    If we did not want to use the page slug, we could use a custom field eg: body_class, on the top level page and set the class in the post meta.

    </head>

<?php
$class = '';
if( is_page() ) {
	global $post;
	$parents = get_post_ancestors( $post->ID );
	$id = ($parents) ? $parents[count($parents)-1]: $post->ID;
	$class = get_post_meta( $id, 'body_class', true );
}
?>

<body <?php body_class( $class ); ?>>
  4. Skip to note 8 content
    Brandon Zhang
    You must log in to vote on the helpfulness of this noteVote results for this note: 0You must log in to vote on the helpfulness of this note

    Suppose we have this pages structure:

    • Top level page (ID: 107)
      • 2nd level page (ID: 997)
        • 3rd level page (ID: 1090)
          • Current post

    [0] => int(1090) [1] => int(997) [2] => int(107)

    So, if you want to get its direct parent page, then use the first element, or use the last element if you want to get the top level page.

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