redirect_canonical example

    $redirect_url = apply_filters( 'redirect_canonical', $redirect_url, $requested_url );

    // Yes, again -- in case the filter aborted the request.     if ( ! $redirect_url || strip_fragment_from_url( $redirect_url ) === strip_fragment_from_url( $requested_url ) ) {
        return;
    }

    if ( $do_redirect ) {
        // Protect against chained redirects.         if ( ! redirect_canonical( $redirect_url, false ) ) {
            wp_redirect( $redirect_url, 301 );
            exit;
        } else {
            // Debug.             // die("1: $redirect_url<br />2: " . redirect_canonical( $redirect_url, false ) );             return;
        }
    } else {
        return $redirect_url;
    }
}