Erik Aybar

PHP Autoloading with Composer (an intro)

May 07, 2014

This is going to be a simplified, high-level look at:

  • Using Composer for dependency management in PHP projects
  • Using Composer’s beautiful autoload directive
  • Possibly a glimpse of getting started with PHPUnit for unit testing our application

We will be building a simple Calculator app Useless application…

The examples illustrated here are admittely useless, but imagine building an application with hundreds of classes and a complex directory structure. Would you really want to maintain a disgusting amount of require 'the/path/to/my/Class.php'; statments?

I thought not. Hence Composer.

The source: GitHub Repo


Install Composer

First, we need to install composer. This is an extremely simple process outlined in The Composer Docs. I recommend following the global installation instructions so you can use the command in any project/directory

$ curl -sS | php
$ mv composer.phar /usr/local/bin/composer
$ # Yes... that is all :)

Setup our development directory

mkdir OurDirectory; cd OurDirectory
git init
git add .
git commit -m "Initial Commit"
git checkout -b develop

The First Steps with Composer

For now, we are going to stick strictly with Composer’s autoloading feature. If you’ve been developing modern PHP applications, chances are you’ve either been using Composer’s autoloading feature or you’ve been resorting to methods of which I will refrain from comment.

We could do this all manually… in fact, since it is so simple, we will. Just know that a simple composer init would generate such a file.

In our project’s root, we will create a composer.json file that looks something like this…


    "autoload": {


Now run composer install

and!… well, not a whole lot happened. Baby steps…

Composer generates some files...

Now fast forward a bit…

  • Create src/classmap_dir
  • Create a class to test our autloading LoadMe.php
  • Add ‘classmap’ directive to our composer’s autoload directive

Composer’s Autoloading Reference

Now Fire it Up!

For simplicity’s sake I will be using PHP’s built in web server.

PHP’s built in web server?!

In case you didn’t know (and I wish I would have known earlier). A nifty feature baked in since … oh, 5.4-ish. You can use
php -S localhost:8080

This will set the document root to the current directory.

In my case I am using
php -S localhost:8080 -t src # -t sets the document root to … in this case ‘src’
I’ve put together a simple index.php for us to use as a playground environment. I’ve instantiated our new LoadMe class, fired it up and! …

Fatal error: Class ‘LoadMe’ not found in…

Ok, so we skipped a step. That magic “Autoloading” that everyone keeps talking about… we need to somehow implement that. Now this isn’t the best way (in fact it may be the worst), but let’s start at the basics.

We will go ahead and require '../vendor/autoload.php'; in our index.php and!…

Fatal error: Class ‘LoadMe’ not found in…

Ok, so we have one more step (I promise, we are doing this the hardway to begin with…)

Go ahead and type composer dump-autoload into your fancy terminal and!…

Hello Sir

Houston, we have autoloading.

So at this point we are utlizing the classmap directive in our autoloading and now we can simply

  • Add a class (i.e. MyClass.php) to our src/classmap_dir
  • Run composer dump-autoload
  • Instantiate our class as needed throughout our awesome application index.php file

And we end up with…

The beautiful end result

A snapshot of our file structure and what we have set up so far

The source: GitHub Repo

Note to reader: Using classmap is not ideal. Just skip straight to using PSR-4 in place of classmap. I will do my best to continue this series … I may not. I’m sure you can figure it out ;).

If you are working with PHP at all it is definitely worth your time. Great resource Google “php autoloading with composer”

Read More about Autoloading and PSR autloading here

Erik Aybar

👋🏽 Hi! I'm Erik Aybar. I'm a software person working remotely from St. George, Utah. This is my blog.