CODE EXAMPLE FOR PHP

wp register_setting access saved value

// ACCESS SETTING:
get_option( 'sd_fields' );

// REGISTER SETTING:
function sd_register_settings(){
	register_setting( 
      'sd_option_group',
      'sd_fields', // <== REGISTER
      'sd_callback_function' );
}
add_action( 'admin_init', 'sd_register_settings' );