Show Widgets Only to Logged-In or Logged-Out Visitors

add_action( 'in_widget_form', function ( $widget, $return, $instance ) {
    $value   = isset( $instance['wpide_visibility'] ) ? $instance['wpide_visibility'] : '';
    $options = array(
        ''           => 'Everyone',
        'logged_in'  => 'Logged-in users',
        'logged_out' => 'Logged-out visitors',
    );

    echo '<p><label for="' . esc_attr( $widget->get_field_id( 'wpide_visibility' ) ) . '">Show to:</label> ';
    echo '<select class="widefat" id="' . esc_attr( $widget->get_field_id( 'wpide_visibility' ) ) . '" name="' . esc_attr( $widget->get_field_name( 'wpide_visibility' ) ) . '">';

    foreach ( $options as $key => $label ) {
        echo '<option value="' . esc_attr( $key ) . '"' . selected( $value, $key, false ) . '>' . esc_html( $label ) . '</option>';
    }

    echo '</select></p>';
}, 10, 3 );

add_filter( 'widget_update_callback', function ( $instance, $new_instance ) {
    $value = isset( $new_instance['wpide_visibility'] ) ? sanitize_key( $new_instance['wpide_visibility'] ) : '';

    $instance['wpide_visibility'] = in_array( $value, array( 'logged_in', 'logged_out' ), true ) ? $value : '';

    return $instance;
}, 10, 2 );

add_filter( 'widget_display_callback', function ( $instance ) {
    if ( ! is_array( $instance ) || empty( $instance['wpide_visibility'] ) ) {
        return $instance;
    }

    if ( 'logged_in' === $instance['wpide_visibility'] && ! is_user_logged_in() ) {
        return false;
    }

    if ( 'logged_out' === $instance['wpide_visibility'] && is_user_logged_in() ) {
        return false;
    }

    return $instance;
} );