get_post_thumbnail_id() WordPress Function

function get_post_thumbnail_id( $post = null ) {
	$post = get_post( $post );

	if ( ! $post ) {
		return false;
	}

	$thumbnail_id = (int) get_post_meta( $post->ID, '_thumbnail_id', true );

	/**
	 * Filters the post thumbnail ID.
	 *
	 * @since 5.9.0
	 *
	 * @param int|false        $thumbnail_id Post thumbnail ID or false if the post does not exist.
	 * @param int|WP_Post|null $post         Post ID or WP_Post object. Default is global `$post`.
	 */
	return (int) apply_filters( 'post_thumbnail_id', $thumbnail_id, $post );
}
Uses	Description
wp-includes/post-thumbnail-template.php:post_thumbnail_id	Filters the post thumbnail ID.
wp-includes/plugin.php:apply_filters()	Calls the callback functions that have been added to a filter hook.
wp-includes/post.php:get_post_meta()	Retrieves a post meta field for the given post ID.
wp-includes/post.php:get_post()	Retrieves post data given a post ID or post object.
Used By	Description
wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php:WP_REST_Posts_Controller::prepare_links()	Prepares links for the request.
wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php:WP_REST_Posts_Controller::prepare_item_for_response()	Prepares a single post output for response.
wp-includes/post-thumbnail-template.php:get_the_post_thumbnail_caption()	Returns the post thumbnail caption.
wp-includes/embed.php:get_oembed_response_data_rich()	Filters the oEmbed response data to return an iframe embed code.
wp-includes/post-thumbnail-template.php:get_the_post_thumbnail_url()	Returns the post thumbnail URL.
wp-admin/includes/media.php:edit_form_image_editor()	Displays the image and editor in the post editor
wp-admin/includes/media.php:get_media_item()	Retrieves HTML form for modifying the image attachment.
wp-includes/post-thumbnail-template.php:has_post_thumbnail()	Determines whether a post has an image attached.
wp-includes/post-thumbnail-template.php:update_post_thumbnail_cache()	Updates cache for thumbnails in the current loop.
wp-includes/post-thumbnail-template.php:get_the_post_thumbnail()	Retrieves the post thumbnail.
wp-includes/post-template.php:prepend_attachment()	Wraps attachment in paragraph tag before content.
wp-includes/media.php:wp_prepare_attachment_for_js()	Prepares an attachment post object for JS, where it is expected to be JSON-encoded and fit into an Attachment model.
wp-includes/media.php:wp_playlist_shortcode()	Builds the Playlist shortcode output.
wp-includes/class-wp-xmlrpc-server.php:wp_xmlrpc_server::mw_getPost()	Retrieve post.
wp-includes/class-wp-xmlrpc-server.php:wp_xmlrpc_server::mw_getRecentPosts()	Retrieve list of recent posts.
wp-includes/class-wp-xmlrpc-server.php:wp_xmlrpc_server::_prepare_post()	Prepares post data for return in an XML-RPC object.
Version	Description
5.5.0	The return value for a non-existing post was changed to false instead of an empty string.
4.4.0	`$post` can be a post ID or WP_Post object.
2.9.0	Introduced.