How to get the root directory of the website in php?

Question

I originally learned java by using <%=request.getContextPath()%> to get the site root directory, but now I’m confused when learning php

java is

< ;a href="<%=request.getContextPath()%>/html/main/main.jsp">Homepage</a></span>

How to write php

Answer 1

You can use $_SERVER['DOCUMENT_ROOT'] to get

Answer 2

PHP has a magic constant __FILE__ that can be obtained