session_start(): Cannot send session cache limiter - headers already sent

Warning: session_start(): Cannot send session cache limiter - headers already sent (output started at /data/home/htdocs/update.php:1) in /data/home/htdocs/admin.php on line 3 131

解决方案：
一、将 session_start() 放在最顶部；
二、检查文件是否为 UTF-8-BOM 并修改为 UTF-8 即可。