non-cmb2-options-page.php

<?php
/**
 * Adding standard WP Settings API options page as sub-menu item to CMB2 Tabs.
 *
 * @see https://developer.wordpress.org/plugins/settings/custom-settings-page/
 *
 * @internal never define functions inside callbacks.
 * these functions could be run multiple times; this would result in a fatal error.
 */

/**
 * custom option and settings
 */
function wporg_settings_init() {
	// Register a new setting for "wporg" page.
	register_setting( 'wporg', 'wporg_options' );

	// Register a new section in the "wporg" page.
	add_settings_section(
		'wporg_section_developers',
		__( 'The Matrix has you.', 'wporg' ), 'wporg_section_developers_callback',
		'wporg'
	);

	// Register a new field in the "wporg_section_developers" section, inside the "wporg" page.
	add_settings_field(
		'wporg_field_pill', // As of WP 4.6 this value is used only internally.
		// Use $args' label_for to populate the id inside the callback.
		__( 'Pill', 'wporg' ),
		'wporg_field_pill_cb',
		'wporg',
		'wporg_section_developers',
		array(
			'label_for'         => 'wporg_field_pill',
			'class'             => 'wporg_row',
			'wporg_custom_data' => 'custom',
		)
	);
}

/**
 * Register our wporg_settings_init to the admin_init action hook.
 */
add_action( 'admin_init', 'wporg_settings_init' );


/**
 * Custom option and settings:
 *  - callback functions
 */


/**
 * Developers section callback function.
 *
 * @param array $args  The settings array, defining title, id, callback.
 */
function wporg_section_developers_callback( $args ) {
	?>
	<p id="<?php echo esc_attr( $args['id'] ); ?>"><?php esc_html_e( 'Follow the white rabbit.', 'wporg' ); ?></p>
	<?php
}

/**
 * Pill field callbakc function.
 *
 * WordPress has magic interaction with the following keys: label_for, class.
 * - the "label_for" key value is used for the "for" attribute of the <label>.
 * - the "class" key value is used for the "class" attribute of the <tr> containing the field.
 * Note: you can add custom key value pairs to be used inside your callbacks.
 *
 * @param array $args
 */
function wporg_field_pill_cb( $args ) {
	// Get the value of the setting we've registered with register_setting()
	$options = get_option( 'wporg_options' );
	?>
	<select
		id="<?php echo esc_attr( $args['label_for'] ); ?>"
		data-custom="<?php echo esc_attr( $args['wporg_custom_data'] ); ?>"
		name="wporg_options[<?php echo esc_attr( $args['label_for'] ); ?>]"
	>
		<option value="red" <?php echo isset( $options[ $args['label_for'] ] ) ? ( selected( $options[ $args['label_for'] ], 'red', false ) ) : ( '' ); ?>>
		<?php esc_html_e( 'red pill', 'wporg' ); ?>
		</option>
		<option value="blue" <?php echo isset( $options[ $args['label_for'] ] ) ? ( selected( $options[ $args['label_for'] ], 'blue', false ) ) : ( '' ); ?>>
		<?php esc_html_e( 'blue pill', 'wporg' ); ?>
		</option>
	</select>
	<p class="description">
		<?php esc_html_e( 'You take the blue pill and the story ends. You wake in your bed and you believe whatever you want to believe.', 'wporg' ); ?>
	</p>
	<p class="description">
		<?php esc_html_e( 'You take the red pill and you stay in Wonderland and I show you how deep the rabbit-hole goes.', 'wporg' ); ?>
	</p>
	<?php
}

/**
 * Add the top level menu page.
 */
function wporg_options_page() {
	add_submenu_page(
		'yourprefix_theme_options',
		'WPOrg',
		'WPOrg Options',
		'manage_options',
		'wporg',
		'wporg_options_page_html'
	);
}


/**
 * Register our wporg_options_page to the admin_menu action hook.
 */
add_action( 'admin_menu', 'wporg_options_page' );


/**
 * Top level menu callback function
 */
function wporg_options_page_html() {
	// check user capabilities
	if ( ! current_user_can( 'manage_options' ) ) {
		return;
	}

	// add error/update messages

	// check if the user have submitted the settings
	// WordPress will add the "settings-updated" $_GET parameter to the url
	if ( isset( $_GET['settings-updated'] ) ) {
		// add settings saved message with the class of "updated"
		add_settings_error( 'wporg_messages', 'wporg_message', __( 'Settings Saved', 'wporg' ), 'updated' );
	}

	$cmb    = cmb2_get_metabox( 'yourprefix_theme_options_page' );
	$hookup = new CMB2_Options_Hookup( $cmb, 'yourprefix_theme_options' );

	// show error/update messages
	settings_errors( 'wporg_messages' );
	?>
	<div class="wrap">
		<h1><?php echo esc_html( get_admin_page_title() ); ?></h1>
		<?php $hookup->options_page_tab_nav_output(); ?>
		<form action="options.php" method="post">
			<?php
			// output security fields for the registered setting "wporg"
			settings_fields( 'wporg' );
			// output setting sections and their fields
			// (sections are registered for "wporg", each field is registered to a specific section)
			do_settings_sections( 'wporg' );
			// output save settings button
			submit_button( 'Save Settings' );
			?>
		</form>
	</div>
	<?php
}

function wporg_options_page_to_cmb2_tabs( $tabs, $tab_group ) {
	if ( 'yourprefix_theme_options' === $tab_group ) {
		$tabs['wporg'] = 'WPOrg';
	}

	return $tabs;
}

add_filter( 'cmb2_tab_group_tabs', 'wporg_options_page_to_cmb2_tabs', 10, 2 );