_wp_preview_post_thumbnail_filter( null|array|string $value, int $post_id, string $meta_key )

This function’s access is marked private. This means it is not intended for use by plugin or theme developers, only in other core functions. It is listed here for completeness.

Filters post thumbnail lookup to set the post thumbnail.

Parameters

$value

(null|array|string) (Required) The value to return

  • a single metadata value, or an array of values.

$post_id

(int) (Required) Post ID.

$meta_key

(string) (Required) Meta key.

Return

(null|array) The default return value or the post thumbnail meta array.

Source

File: wp-includes/revision.php 

function _wp_preview_post_thumbnail_filter( $value, $post_id, $meta_key ) {
	$post = get_post();
	if ( ! $post ) {
		return $value;
	}

	if ( empty( $_REQUEST['_thumbnail_id'] ) ||
		empty( $_REQUEST['preview_id'] ) ||
		$post->ID != $post_id ||
		'_thumbnail_id' !== $meta_key ||
		'revision' === $post->post_type ||
		$post_id != $_REQUEST['preview_id'] ) {

		return $value;
	}

	$thumbnail_id = (int) $_REQUEST['_thumbnail_id'];
	if ( $thumbnail_id <= 0 ) {
		return '';
	}

	return (string) $thumbnail_id;
}

Uses

Uses Description
wp-includes/post.php: get_post()

Retrieves post data given a post ID or post object.

Changelog

Version Description
4.6.0 Introduced.

© 2003–2021 WordPress Foundation
Licensed under the GNU GPLv2+ License.
https://developer.wordpress.org/reference/functions/_wp_preview_post_thumbnail_filter