CI框架 Cannot modify header information - headers already sent by

A PHP Error was encountered

Severity: Warning

Message: Cannot modify header information - headers already sent by (output started at /var/www/fbz/application/models/Content.php:268)

Filename: helpers/url_helper.php

貌似把前面的

$logsession = $this->session->all_userdata();

这句去了也不会报错

回复内容：

A PHP Error was encountered

Severity: Warning

Message: Cannot modify header information - headers already sent by (output started at /var/www/fbz/application/models/Content.php:268)

Filename: helpers/url_helper.php

貌似把前面的

$logsession = $this->session->all_userdata();

这句去了也不会报错

因为在使用session前已经有输出了
一般是因为php文件?>结尾后有空格回车
或者使用了echo或print