In the http transmission text, it is stipulated that the order of header and content must be: header before content, and header format must satisfy the format of “keyword: value\n”.

1. If there is any output content before the output of header, it will cause a wrong understanding of header (although it is now error tolerant). For example, if the format “keyword: value\n” is not satisfied, it will be directly wrong, but after the format “keyword: value\n” is satisfied, will the client install the wrong understanding or correct understanding?

2. When session is enabled, it is implied whether header(” Set-Cookie: sid=xxxxxx ”) is used for triggering, which means that it is actually an implicit header call