Retrieves the post thumbnail ID.

Parameters

$postint|WP_Postoptional

Post ID or WP_Post object. Default is global $post.

Default:null

Return

More Information

• To enable featured images, see post thumbnails, the current theme must include add_theme_support( 'post-thumbnails' ); in its functions.php file. See also Post Thumbnails.
• “Post Thumbnail” is an outdated term for “Featured Image”. This function returns the ID of the post’s featured image. It does not return IDs of other images attached to posts that are thumbnail sized.

Source

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 );
}

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Hooks

apply_filters( ‘post_thumbnail_id’, int|false $thumbnail_id, int|WP_Post|null $post )

Filters the post thumbnail ID.

Changelog