为什么在doctype上方有PHP代码？

Question

I'm still learning this stuff, but for the most part, my understanding is that you want code in the head or the body. I'm working with a page that is a login page.

Above the doctype is all the php code for the login validation checking and the "root.php" include which is declaring the root of the project, etc.

Is this the way things should be done?

If I move the doctype to the top, I get an error. As it is, the browser sees the doctype as the top item when I view source.

So my question is when would I want to put code above the doctype?

Answer 1

标头需要在第一个html输出之前发送，因此，例如，如果要使用session_start（），则需要在发送第一个文本之前发送。