1.Warning: Cannot modify header information - headers already sent by
2.Warning: session_start(): Cannot send session cookie - headers already sent by
3.Warning: session_start(): Cannot send session cache limiter - headers already sent
提示这样的错误，有两种解决办法:
1.把php代码
header("Cache-Control: no-store, no-cache, must-revalidate");
session_start();
放在代码的最上面，前面不能有空格或html等任何代码
2.修改php.int output_buffering = on 把off改成on

关键词：php