The reason why there cannot be output before header and session_start in PHP_PHP Tutorial

The reason why there cannot be output before header and session_start in PHP is analyzed below.

In the http transmission text, it is stipulated that the order of header and content must be: header first and content last, and the format of the header must meet the format of "keyword: valuen".

1. If there is output content before the header is output, it will cause a misunderstanding of the header (although it is now fault-tolerant). For example, if it does not meet the format of "keyword: valuen", it is fine, but it is directly wrong, but it does satisfy After the "keyword: valuen" format, does the client install the wrong interpretation, or does it follow the correct interpretation?

2. When the session is opened, it will implicitly trigger whether to use header ("Set-Cookie: sid=xxxxxx"), which is actually an implicit header call

http://www.bkjia.com/PHPjc/632157.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/632157.htmlTechArticleThe reason why there cannot be output before header and session_start in PHP is analyzed below. In the http transmission text, it is stipulated that the order of header and content must be: header first, content first...