How do I correctly autoload classes OS-safe with namespaces?

Question

I am looking for the cleanest, most elegant way to build OS-safe path strings in PHP 8 and include them in my autoload function, without str_replace() or substr(), if possible.

I have a file structure like this:

NameOfProject
├──(...)
├──src
|  ├──Controller
|  |  └──(...)
|  ├──Helper
|  |  └──(...)
|  ├──Model
|  |  └──(...)
|  ├──View
|  |  └──(...)
└──index.php

Every class in the src folder is namespaced accordingly, for example NameOfProject\src\Controller. I want to autoload every class, using the spl_autoload_register() function.

This is my code:

<?php
//index.php

spl_autoload_register(function($class)
{
  include
    dirname(__FILE__, 2)
    .'/'
    .str_replace('\\', '/', $class)
    .'.php';
});

I am wondering if there is a more elegant way to avoid the str_replace(), but without it, the concatenation of the path string doesn't work, because $class always returns the namespace (with backslash) and not the actual path.

I have read that PHP already transforms forward slashes / to DIRECTORY_SEPARATOR within functions, but I think I remember having an issue with using just forward slashes in the past.

If the str_replace() has to be there, maybe using DIRECTORY_SEPARATOR is in order? Like so:

str_replace('\\', DIRECTORY_SEPARATOR, $class)

I have also considered the option to strip the class name from $class, but this, too, requires an "ugly" substr():

$class = substr($class, strrpos($class, "\\") + 1);

Answer 1

If your code structure is very neat, you can just use the default autoload implementation, see notes in this page:

set_include_path('parent folder of NameOfProject');
spl_autoload_register();

This method will try to load the class NameOfProject\src\Controller\MyController from nameofproject/src/controller/mycontroller.php.