A basic example of PSR-4 Autoloading with Composer
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Composer PSR-4 Example

When attempting to learn how to use namespaces in PHP combined with Composer's PSR-4 autoloading spec, I couldn't find a solid working example. I understood the theory of autoloading, I understood why Namespaces were good - I just wanted a working template so I could start coding.

Well, I couldn't find one, so I'm making one.


Install the dependencies (currently only phpunit)

$ php composer.phar install

Run the unit test to verify everything works correctly

~$ ./vendor/bin/phpunit tests/

You should see the following output

PHPUnit 4.8.16 by Sebastian Bergmann and contributors.


Time: 41 ms, Memory: 3.75Mb

OK (1 test, 1 assertion)

How to use namespaces with Composer

Suppose you want to create a namespace named MyNameSpace

  1. Map MyNameSpace to a base directory via the composer.json file
  2. Within the base directory for the namespace, create a php file named MyClass.php
  3. Inside MyClass.php, declare the namespace MyNameSpace
  4. Inside MyClass.php, ensure the class MyClass has been defined, and that it matches the php file name exactly
  5. Files that wish to use MyClass can now access it via use MyNameSpace\MyClass.

Adding/editing namespaces

Any time you update composer.json with new namespace information, you must run an update.

$ php composer.phar update