src/Post.php
public function featured_image_id() {
		if ( isset( $this->featured_image_id ) ) {
			return $this->featured_image_id;
		}
		$this->featured_image_id = \get_post_thumbnail_id( $this->post );
		return $this->featured_image_id;
	}
public function featured_image_id() {
		if ( isset( $this->featured_image_id ) ) {
			return $this->featured_image_id;
		}
		$this->featured_image_id = \get_post_thumbnail_id( $this->post );
		return $this->featured_image_id;
	}
public function featured_image_id ( ) { if ( isset ( $ this -> featured_image_id ) ) { return $ this -> featured_image_id ; } $ this -> featured_image_id = \ get_post_thumbnail_id ( $ this -> post ) ; return $ this -> featured_image_id ; }
Returns Featured Image ID.

@return bool|int|mixed|string
Returns Featured Image ID .