WordPress options as array

<?php
/*
Plugin Name: WordPress Options Example
Description: WordPress options page example for a question asked in <a href="https://www.facebook.com/groups/1709897292614128">WordPress For Developers Group</a>
Plugin URI: https://www.facebook.com/groups/1709897292614128
Author: Yehuda Hassine
Author URI: https://www.facebook.com/groups/1709897292614128
Version: 1.0
License: GPL2
*/
register_activation_hook( __FILE__, 'yh_activate' );
function yh_activate() {
    add_option( 'yh_options_example', array( 'firstname' => '', 'lastname' => '' ) );
}

register_deactivation_hook( __FILE__, 'yh_deactivate' );
function yh_deactivate() {
    delete_option( 'yh_options_example' );
}

add_action( 'admin_menu', 'yh_add_options_page' );
function yh_add_options_page() {
    add_options_page( 'WordPress Options Example', 'WordPress Options Example', 'manage_options', 'yh', 'render_options_page' );
}

function render_options_page() {
    ?>
    <div class="wrap">
        <?php
        $options = get_option( 'yh_options_example' );

        if ( isset( $_POST['submit'] ) && isset( $_POST['data'] ) ) {
            $data = array_map( 'sanitize_text_field', wp_unslash( $_POST['data'] ) );

            update_option( 'yh_options_example', $data );
            ?>
            <div id="setting-error-settings_updated" class="updated settings-error notice is-dismissible">
                <p>
                    <strong>Settings saved.</strong>
                </p>
                <button type="button" class="notice-dismiss">
                    <span class="screen-reader-text">Dismiss this notice.</span>
                </button>
            </div>
        <?php } ?>
        <form action="" method="post">
            <label for="firstname">
                <input type="text" id="firstname" name="data[firstname]" value="<?php echo show_option( $options['data']['firstname'] ); ?>" />
            </label>
            <label for="lastname">
                <input type="text" id="lastname" name="data[lastname]" value="<?php echo show_option( $options['data']['lastname'] ); ?>" />
            </label>
            <button class="button button-primary" type="submit" name="submit">Submit</button>
        </form>
    </div>
    <?php
}

function show_option( $option ) {
    if ( $option && ! empty( $option ) ) {
        return esc_attr( $option );
    } else {
        return '';
    }
}