How to use spl_autoload_register for multiple diectories in PHP?

Question

I'm actually trying to create a MVC framework for my own, however I'm having troubles with the Autoload. It's not a problem actually, but I'd like to ask the gurus, how are they using the spl_autoload_register function when there are different directories.

Lets say we have the following directories:

Controllers
Libs
Models

Each folder contains different classes, like:

Controllers:
   Main.php
   File.php
   About.php
Libs:
   Main.php
   Front_controller.php
Models:
   Index.php
   File.php
   Login.php

You can notice that some file names might be found with the same name in different directories. Okay, so this is what I've tried so far:

spl_autoload_register(function ($class) { 

    $pathContorllers = 'Controllers/' . $class . '.php';
    $pathLibs = 'Libs/' . $class . '.php';
    $pathModels = 'Models/' . $class . '.php';

    if (file_exists($pathContorllers)) {
        require_once $pathContorllers;
    } elseif (file_exists($pathLibs)) {
        require_once $pathLibs;
    } elseif (file_exists($pathModels )) {
        require_once $pathModels ;
    }
});

It is working well, however I'm sure that there is another way to make everything simpler. Can anyone suggest me how can I make this code better or simpler / what are gurus using in this situation?

Answer 1

For the purpose of keeping individuals who may come across this answer from obtaining out-of-date information I have updated it in regards to the latest PSR autoloading standards. The original answer has been maintained for historical purposes and for those who are only interested in the PSR-0 autoloader.

Updated Answer

The PHP-FIG has officially deprecated the PSR-0 standard in favor of the alternative autoloader, PSR-4. Although the two are similar in some aspects they are also very different in others. (E.g.: the handling of underscores in class names.)

You may be thinking to yourself -- "I use PSR-0 now and it works fine." The truth of the matter is that PSR-0 will still work fine for certain projects. This is especially true when backwards compatibility with a package that doesn't use namespaces is concerned. PSR-0 is still a decent autoloading principle, but it has its own shortcomings.

Of course, if there is one thing that is a constant with programming, it is that code eventually changes and programming techniques continue to evolve. You can do yourself a favor today by preparing yourself for tomorrow. Therefore, if you are just starting a project or are trying to port a project to a newer version of PHP that can use namespaces, you should seriously consider using the PSR-4 autoloader.

It is also worth noting that if you are developing a project that does not use namespaces then PSR-4 does not apply to you. In this case PSR-0 or your own custom autoloader applies.

---

Original Answer

If you want to go with namespaces in your classes, then the PSR-0 route is a pretty good way to autoload. Basically your namespace represents you directory structure and classes can be loaded based on a convention.

If the PSR-0 method doesn't meet all your needs (or doesn't play nice with existing code) you can still add more functions with spl_autoload_register and PHP will go through them one by one in an attempt to load classes.

Example usage:

First thing is first, if you aren't familiar with namespaces in PHP then you will benefit from checking out the PHP manual on the subject. They can be a bit confusing at first, but their benefits are worth the initial confusion.

So I said that PSR-0 works by associating your namespaces with your directory structure. Let's use your directories for an example. You have in your root folder (wherever it may be) the following:

Project directory:  <- Let's call this directory "MyProject"
    Controllers:
       Main.php
       File.php
       About.php
    Libs:
       Main.php
       Front_controller.php
    Models:
       Index.php
       File.php
       Login.php
index.php <- Let's say this is your entry point file, this is where you will be autoloading stuff from.

Now let's take a look at your controller Main.php. Two things to keep in mind is that the class name needs to be the name of the file and the namespace for that class is the directory path to that file. So Main.php should look something like this:

<?php

namespace MyProject\Controllers;

class Main {

    //Field vars, contructor, methods, etc. all go here.
    
}

?>

You would do the same thing for your your Login model

<?php

namespace MyProject\Models;

class Login {

    //Field vars, contructor, methods, etc. all go here.
    
}

?>

Now in your index.php file (out in the root directory - MyProject) you would make your call to the spl_autoload_register and give it the PSR-0 autoloader.

spl_autoload_register( function ($className) {
    $className = ltrim($className, '\\');
    $fileName  = '';
    $namespace = '';
    if ($lastNsPos = strrpos($className, '\\')) {
        $namespace = substr($className, 0, $lastNsPos);
        $className = substr($className, $lastNsPos + 1);
        $fileName  = str_replace('\\', DIRECTORY_SEPARATOR, $namespace) . DIRECTORY_SEPARATOR;
    }
    $fileName .= str_replace('_', DIRECTORY_SEPARATOR, $className) . '.php';

    require $fileName;
});

//Now you can make your call to your objects without a bunch of include/require statements

$main = new \MyProject\Controllers\Main();  //Instantiates your 'Main' controller
$login = new \MyProject\Models\Login();   //Instantiates your 'Login' model

Hopefully that helps make better sense of it, and again, if you don't want to use namespaces you can always just keep adding closures into the SPL autoload stack. You can have 10 different autoloaders in there if you want and PHP will go through them one by one (in the order you defined them) using each function to try and load a class. However, a couple convention based autoloaders is a bit cleaner and more of a preferred method. Also keep in mind that the autoloader translates both namespace separators \ and underscores _ as a directory separator. So your Front_controller.php would not autoload as you would expect.

Answer 2

The code below will help. But I'll advice you check on Namespaces.

spl_autoload_register ( function ($class) {

$sources = array("Controllers/$class.php", "Lib/$class.php ",  "Models/$class.php " );

    foreach ($sources as $source) {
        if (file_exists($source)) {
            require_once $source;
        } 
    } 
});