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_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.

Description

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 ) {
	if ( ! $post = get_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 = intval( $_REQUEST['_thumbnail_id'] );
	if ( $thumbnail_id <= 0 ) {
		return '';
	}

	return strval( $thumbnail_id );
}

Changelog

Version Description
4.6.0 Introduced.

© 2003–2019 WordPress Foundation
Licensed under the GNU GPLv2+ License.
https://developer.wordpress.org/reference/functions/_wp_preview_post_thumbnail_filter