Composer autoload mechanism in PHP - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of Composer's autoload mechanism?

Composer's autoload mechanism automatically loads PHP classes when they are needed, so you don't have to manually include or require class files.

beginner

Which file does Composer generate to handle autoloading?

Composer generates a file called vendor/autoload.php that you include in your project to enable autoloading of classes.

beginner

How do you include Composer's autoload file in your PHP script?

Use require 'vendor/autoload.php'; at the beginning of your PHP script to enable autoloading.

intermediate

What are PSR-4 and PSR-0 in the context of Composer autoloading?

PSR-4 and PSR-0 are standards for autoloading PHP classes based on namespaces and file paths. Composer supports these to map namespaces to directories automatically.

intermediate

How do you define autoloading rules in Composer?

You define autoloading rules in the composer.json file under the autoload section, specifying namespaces and their corresponding directories.

What file must you include to use Composer's autoloading?

A index.php

B composer.json

C autoload.php

D vendor/autoload.php

Composer generates the vendor/autoload.php file to handle autoloading of classes.

Which autoloading standard maps namespaces to directory paths?

A PSR-7

B PSR-4

C PSR-1

D PSR-12

PSR-4 defines how namespaces correspond to directory structures for autoloading.

Where do you specify autoloading rules in a Composer project?

A composer.json under autoload

B vendor/composer.lock

C index.php

D php.ini

The autoload section in composer.json defines how classes are autoloaded.

What command updates the autoload files after changing composer.json?

A composer dump-autoload

B composer update

C composer install

D composer init

The command 'composer dump-autoload' regenerates the autoload files.

What happens if you forget to include vendor/autoload.php?

A Your PHP script will run faster

B Composer will load classes anyway

C Classes won't load automatically, causing errors

D Nothing, autoloading is optional

Without including vendor/autoload.php, PHP won't know how to load classes automatically.

Explain how Composer's autoload mechanism works and why it is useful.

Think about how PHP finds classes without you writing many include statements.

Describe how to set up PSR-4 autoloading in a Composer project.

Focus on the steps from defining rules to using autoload in your code.