How and where should I use the keyword “use” in php

Question

I used use the keyword \"use\" generally above the class definition. Like this:

Answer 1

use is basically including a class in the file to use it. There are two ways to include a class file in another file. The most general is require or include method. Another method is using composer. Assume this Directory Structure

Project
  |
  |--- Folder A
  |      |
  |      |---UserRegistration.php
  |
  |---Example
         |
         |--TestUserRegistration.php    

In Folder A there is UserRegistartion.php and you want to use the code in TestUserRegistration.php In UserRegistration.php It can be class, trait or Interface

Method 1.

In TestUserRegisteration.php you can include or require file UserRegistartion.php
and use it

Method 2

Using Composer. In UserRegistration.php you define namespace FolderA; as the first line of code. Then write your code as you do. So Now you want to use this file in TestUserRegistration.php you do

include vendor/autoload.php;
use FolderA\UserRegistration;

Which one is better and why?

Method 2 using composer is the best method. In method 1 wherever you want to include UserRegistration you have to find the relative path to UserRegistration file. So lets assume some day you need to change the directory structure your application will break as the relative path you had provided now it does'nt exist.

But in Method 2 you always use the namespace you provided \ The filename instead of where you want to use. So even you change the directory structure you don't have to got all codes and modify the path. It will work as it was. To know more study about how to use namespace and composer.