Obtener categoría primaria de Yoast

if ( ! function_exists( 'get_primary_taxonomy' ) ) {
	function get_primary_taxonomy( $post_id, $taxonomy ) {
		$prm_term = '';
		if (class_exists('WPSEO_Primary_Term')) {
			$wpseo_primary_term = new WPSEO_Primary_Term( $taxonomy, $post_id );
			$prm_term = $wpseo_primary_term->get_primary_term();
		}
		if ( !is_object($wpseo_primary_term) && empty( $prm_term ) ) {
			$term = wp_get_post_terms( $post_id, $taxonomy );
			if (isset( $term ) && !empty( $term ) ) {
				return wp_get_post_terms( $post_id, $taxonomy )[0]->term_id;
			} else {
				return '';
			}
		}
		
		return get_term($wpseo_primary_term->get_primary_term(),$taxonomy);
	}
}