use vs include as an import statement in PHP

Question

I have 2 simple files:

file1.php

<?php
namespace NM\data;
class MyClass
{
    static function myStaticFunction(){
        echo __NAMESPACE__." heheh";
    }
}
function myfunction()
{
    echo __FUNCTION__." some data";
}
const MYCONST = 1;

and file2.php:

<?php
// include 'file1.php';
use NM\data as NM;
class MyClass
{
}
function myfunction()
{
    echo __NAMESPACE__." heheh";
}
const MYCONST = 2;
echo NM\myfunction();

The docs say that you can use use as an importing command for namespaces. http://php.net/manual/en/language.namespaces.importing.php

I had little success with importing namespaces with just use. For some other namespace to be used, I had to use include. But if I use include, than use is performs just an alias.

Is is possible to import a namespace just with the use keyword?

Answer 1

But if I use include, than use is performs just an alias.

Yup, that's all use does. use just aliases namespaces. No more, no less. It is orthogonal to actually loading any piece of code from a file.

Answer 2

Actually there is a way to do so. Read about autoload functions in PHP, I would suggest to look on PSR-4 Autoloading

Before PHP 5.3 there was no namespace-s so files ware loaded by include function. On that time we had PSR-0 which loaded files by it's name but this was leading to long class names like "Mage_Admin_Model_Block". (this was resolved to file located in directory "Mage/Admin/Model/Block.php"

With namespaces introduced in php 5.3+ new autoloading standard was introduced, it is using namespaces to resolve path to file that contains definition of class that we want to use.

For example this use Symfony\Bundle\FrameworkBundle\Controller\Controller

is resolved to: 'Symfony\Bundle\FrameworkBundle\Controller\Controller.php`

So PHP does not know where class file is located but with use of autoloader it can resolve where that file is present and load it if needed. You can write you're own code to do so but i would strongly suggest to stick to PSR-4 standard (PSR-0 is outdated now)