gistfile1.txt

add_action( 'cmb2_init', 'yourprefix_register_about_page_metabox' );
/**
 * Hook in and add a metabox that only appears on the 'About' page
 */
function yourprefix_register_about_page_metabox() {

	// Start with an underscore to hide fields from custom fields list
	$prefix = '_yourprefix_about_';

	/**
	 * Metabox to be displayed on a single page ID
	 */
	$cmb_about_page = new_cmb2_box( array(
        'id'           => 'contact-information',
        'title'        => 'Contact Information',
        'object_types' => array( 'page' ), // post type
        'cmb2_show_on'      => array( 'key' => 'page-template', 'value' => 'page-nosidebar.php' ),
        'context'      => 'normal', //  'normal', 'advanced', or 'side'
        'priority'     => 'high',  //  'high', 'core', 'default' or 'low'
        'show_names'   => true, // Show field names on the left
    ) );

	$cmb_about_page->add_field( array(
		'name' => __( 'Test Text', 'cmb2' ),
		'desc' => __( 'field description (optional)', 'cmb2' ),
		'id'   => $prefix . 'text',
		'type' => 'text',
	) );
}




/**
 * Metabox for Page Template
 * @author Kenneth White
 * @link https://github.com/WebDevStudios/CMB2/wiki/Adding-your-own-show_on-filters
 *
 * @param bool $display
 * @param array $meta_box
 * @return bool display metabox
 */
function be_metabox_show_on_template( $display, $meta_box ) {
    if ( ! isset( $meta_box['show_on']['key'], $meta_box['show_on']['value'] ) ) {
        return $display;
    }

    if ( 'template' !== $meta_box['show_on']['key'] ) {
        return $display;
    }

    $post_id = 0;

    // If we're showing it based on ID, get the current ID
    if ( isset( $_GET['post'] ) ) {
        $post_id = $_GET['post'];
    } elseif ( isset( $_POST['post_ID'] ) ) {
        $post_id = $_POST['post_ID'];
    }

    if ( ! $post_id ) {
        return false;
    }

    $template_name = get_page_template_slug( $post_id );
    $template_name = ! empty( $template_name ) ? substr( $template_name, 0, -4 ) : '';

    // See if there's a match
    return in_array( $template_name, (array) $meta_box['show_on']['value'] );
}
add_filter( 'cmb2_show_on', 'be_metabox_show_on_template', 10, 2 );

    

gistfile2.txt

add_action( 'cmb2_init', 'yourprefix_register_about_page_metabox' );
/**
 * Hook in and add a metabox that only appears on the 'About' page
 */
function yourprefix_register_about_page_metabox() {

	// Start with an underscore to hide fields from custom fields list
	$prefix = '_yourprefix_about_';

	/**
	 * Metabox to be displayed on a single page ID
	 */
	$cmb_about_page = new_cmb2_box( array(
        'id'           => 'contact-information',
        'title'        => 'Contact Information',
        'object_types' => array( 'page' ), // post type
        'cmb2_show_on'      => array( 'key' => 'page-template', 'value' => 'page-nosidebar.php' ),
        'context'      => 'normal', //  'normal', 'advanced', or 'side'
        'priority'     => 'high',  //  'high', 'core', 'default' or 'low'
        'show_names'   => true, // Show field names on the left
    ) );

	$cmb_about_page->add_field( array(
		'name' => __( 'Test Text', 'cmb2' ),
		'desc' => __( 'field description (optional)', 'cmb2' ),
		'id'   => $prefix . 'text',
		'type' => 'text',
	) );
}




/**
 * Metabox for Page Template
 * @author Kenneth White
 * @link https://github.com/WebDevStudios/CMB2/wiki/Adding-your-own-show_on-filters
 *
 * @param bool $display
 * @param array $meta_box
 * @return bool display metabox
 */
function be_metabox_show_on_template( $display, $meta_box ) {
    if ( ! isset( $meta_box['show_on']['key'], $meta_box['show_on']['value'] ) ) {
        return $display;
    }

    if ( 'template' !== $meta_box['show_on']['key'] ) {
        return $display;
    }

    $post_id = 0;

    // If we're showing it based on ID, get the current ID
    if ( isset( $_GET['post'] ) ) {
        $post_id = $_GET['post'];
    } elseif ( isset( $_POST['post_ID'] ) ) {
        $post_id = $_POST['post_ID'];
    }

    if ( ! $post_id ) {
        return false;
    }

    $template_name = get_page_template_slug( $post_id );
    $template_name = ! empty( $template_name ) ? substr( $template_name, 0, -4 ) : '';

    // See if there's a match
    return in_array( $template_name, (array) $meta_box['show_on']['value'] );
}
add_filter( 'cmb2_show_on', 'be_metabox_show_on_template', 10, 2 );