[Custom side menu] WordPress customizer page side menu

customizer.php

/* Custom side menu -------------------- */

/* Custom side menu section */
$wp_customize->add_section(
	'side_menu_section',
		array(
          'title'		=> __('Side Menu'),
          'description'	=> __('Customize page side menu.'),
          'panel'		=> 'theme_settings',
        )
);
/* Custom size menu setting */
$wp_customize->add_setting(
	'side_menu_name',
		array(
          'default'		=> __('None'),
        )
);
/* Custom size menu control */
$wp_customize->add_control(
  'side_menu_name',
  	array(
      'label'           => __('Menu name'),
      'section'         => 'side_menu_section',
      'priority'        => 1,
    )
);