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What is Composer?

PHP course · Advanced · Lesson 34/92

Learn that Composer is a PHP package manager and what it provides.

What does Composer do?

Composer is a tool that manages external libraries (packages) in PHP projects. When a project needs a logging library like Monolog or an HTTP client like GuzzleHttp, you install them with a single Composer command instead of downloading files by hand and wiring up paths.

Composer also resolves relations between dependencies: if a package needs another, it installs that too automatically. This is called dependency management.

The vendor/ folder and Packagist

When Composer installs, it puts all packages into the vendor/ folder at the project root. You never touch this folder by hand; Composer manages the packages. Packages are published on a public repository called Packagist; Composer searches and downloads from there.

You do not put vendor/ under version control; when another developer runs composer install, the same packages are installed automatically.

Exercise Print the dependency list

Define a $deps array: "monolog/monolog" => "3.5", "guzzlehttp/guzzle" => "7.8", "symfony/console" => "6.4". Print each line in the form monolog/monolog: 3.5.

Show example solution 
" . $ver . "\n"; }.
Example solution:
<?php
$deps = ["monolog/monolog" => "3.5", "guzzlehttp/guzzle" => "7.8", "symfony/console" => "6.4"];
foreach ($deps as $pkg => $ver) {
    echo $pkg . ": " . $ver . "\n";
}

Test yourself

  1. What is Composer's main job?

    • It manages PHP dependencies
    • It speeds up PHP code
    • It backs up databases
    • It captures browser requests
    Show answer

    It manages PHP dependencies — Correct. Composer installs and manages package dependencies.

  2. Complete the Composer command

    <?php
// Composer command to install a package
$cfg = ["cmd" => "____ monolog/monolog"];
echo $cfg["cmd"] . "\n";
    Show answer 
    <?php
// Composer command to install a package
$cfg = ["cmd" => "composer require monolog/monolog"];
echo $cfg["cmd"] . "\n";

  3. Match the Composer concepts

    Composer
    Package manager
    vendor/
    Packages location
    Packagist
    Public repository
    require
    Adds a package

All lessons in Advanced

1 PDO basics

  1. What is PDO?
  2. Connecting with PDO
  3. Running queries with query()
  4. Single row with fetch()
  5. All rows with fetchAll()
  6. Fetch mode constants
  7. Summary - PDO basics

2 Prepared statements

  1. Prepared statements with prepare()
  2. Running with execute()
  3. Binding parameters with bindParam()
  4. Binding values with bindValue()
  5. SQL injection and prevention
  6. Named placeholders
  7. Summary - Prepared statements

3 CRUD operations

  1. Inserting records with INSERT
  2. Reading records with SELECT
  3. Updating records with UPDATE
  4. Deleting records with DELETE
  5. Affected rows with rowCount()
  6. Transaction management
  7. Summary - CRUD operations

4 Project: Blog with PDO

  1. Project: Blog with PDO
  2. Database structure
  3. Adding and listing posts
  4. Editing and deleting posts
  5. Project final - Blog with PDO

5 Namespaces

  1. Defining namespaces
  2. Importing with use
  3. Aliases
  4. Global namespace
  5. Multi-level namespaces
  6. PSR-4 autoloading
  7. Summary - Namespaces

6 Composer

  1. What is Composer?
  2. The composer.json file
  3. Adding packages with require
  4. Autoload (PSR-4)
  5. Installing packages from Packagist
  6. composer update and install
  7. Summary - Composer

7 Regex

  1. Matching with preg_match()
  2. Replacing with preg_replace()
  3. All matches with preg_match_all()
  4. Character classes
  5. Quantifiers
  6. Capture groups
  7. Summary - Regex

8 JSON and API

  1. Encoding with json_encode()
  2. Parsing with json_decode()
  3. JSON error handling
  4. Content-Type with header()
  5. REST API basics
  6. HTTP methods
  7. Summary - JSON and API

9 Project: REST API

  1. Project: REST API
  2. Routing structure
  3. CRUD endpoints
  4. JSON response format
  5. Project final - REST API

10 Security

  1. Hashing with password_hash()
  2. Verifying with password_verify()
  3. SQL injection prevention
  4. XSS prevention
  5. CSRF token generation
  6. Security headers
  7. Summary - Security

11 Middleware

  1. The middleware pattern
  2. Request/Response cycle
  3. Middleware chain
  4. Auth middleware
  5. Logging middleware
  6. PSR-15 basics
  7. Summary - Middleware

12 Testing basics

  1. What is PHPUnit?
  2. Writing your first test
  3. Assertions
  4. Test layout (AAA)
  5. Test doubles (mock, stub)
  6. setUp and tearDown
  7. Summary - Testing basics

13 Design patterns

  1. The Singleton pattern
  2. The Factory pattern
  3. The Observer pattern
  4. The Strategy pattern
  5. The Decorator pattern
  6. The Adapter pattern
  7. Summary - Design patterns

14 Advanced final

  1. Challenge - PDO and API
  2. Challenge - Security app
  3. Challenge - Design patterns
  4. Challenge - Writing tests
  5. Challenge - Mini framework