syntax error, unexpected '['

错误位置

FILE: D:\phpStudy\WWW\User\Home\Controller\LoginController.class.php 　LINE: 60

这是第60行 C( 'mail_setting' )['smtp_server'],

这是60上下附近的 include( 'esmtp.php' );
$smtp = new \esmtp(
C( 'mail_setting' )['smtp_server'],
C( 'mail_setting' )['smtp_server_port'],
true,
C( 'mail_setting' )['smtp_user'],
C( 'mail_setting' )['smtp_pass']


请问如何解决