php-file path problem

1. Background

Today when I was developing a sample website, I encountered a troublesome thing, which was the file path problem of Php. I was very confused. I finally gained some knowledge by checking relevant information!

2. The specific examples are as follows

(1) The URL address of this test is as follows: getallifo.php file under the app folder

http://localhost:8081/GoodsServers/app/getAllIfo.php

(2) Test results

$pa= $_SERVER['DOCUMENT_ROOT']; 
echo $pa;  # D:/Wamp/wamp/www/
echo '<br>';
echo __FILE__; # D:\Wamp\wamp\www\GoodsServers\app\getAllIfo.php
echo '<br>';
echo dirname(__FILE__); # D:\Wamp\wamp\www\GoodsServers\app
echo '<br>';
echo dirname(dirname(__FILE__)); # D:\Wamp\wamp\www\GoodsServers
echo '<br>';
echo basename(__FILE__); # getAllIfo.php
Exit;

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The above has introduced the php-file path problem, including aspects of it. I hope it will be helpful to friends who are interested in PHP tutorials.