你可以像往常一样在任何地方获取和检查你的主题模型的值。

此代码经过测试并正常工作（内部代码cyb_customizer() 正是您在问题中发布的代码，只添加了add_section 零件号）：

function flag_is_custom_excerpt_enabled(){
    $blueplanet_options = get_theme_mod( \'blueplanet_options\');
    if( empty( $blueplanet_options[\'theme_enable_custom_excerpt\'] ) ) {
        return false;
    }
    return true;
}

add_action( \'customize_register\', \'cyb_customizer\' );
function cyb_customizer( $wp_customize ) {


    $wp_customize->add_section(
        \'admin_section\',
        array(
            \'title\' => \'Admin section\',
            \'description\' => \'Admin section\',
            \'priority\' => 0,            
        )
    );

    $wp_customize->add_setting( \'blueplanet_options[theme_enable_custom_excerpt]\',
        array(
            \'default\'    => false,
            \'capability\' => \'edit_theme_options\',
         )
      );
      $wp_customize->add_control(
          \'theme_enable_custom_excerpt\',
          array(
            \'label\'       => \'Enable Custom Excerpt Length\',
            \'section\'     => \'admin_section\',
            \'settings\'    => \'blueplanet_options[theme_enable_custom_excerpt]\',
            \'type\'        => \'checkbox\',
          )
       );
      $wp_customize->add_setting( \'blueplanet_options[theme_custom_excerpt_length]\',
         array(
            \'default\'              => 20,
            \'capability\'           => \'edit_theme_options\',
         )
      );
      $wp_customize->add_control(
          \'theme_custom_excerpt_length\',
          array(
            \'label\'           => \'Custom Excerpt Length\',
            \'section\'         => \'admin_section\',
            \'settings\'        => \'blueplanet_options[theme_custom_excerpt_length]\',
            \'type\'            => \'text\',
            \'active_callback\' => \'flag_is_custom_excerpt_enabled\',
          )
        );

    }