How to Install Composer Laravel on a New Project: 7 Best Practices from the Source Code

The best way to install Composer Laravel on a new project is to use composer create-project, immediately configure your .env file, set proper directory permissions, and verify the installation using Laravel's built-in cache compilation commands.

To install Composer Laravel on a new project correctly, you must follow the framework's specific bootstrap procedures and Composer event hooks. According to the laravel/framework source code, the installation process involves automated cache clearing, environment file loading, and permission checks designed to ensure your application starts in a clean, secure state. Following these framework-level best practices prevents common configuration errors and silent cache failures that can cause deployment issues.

Step 1: Create a Fresh Laravel Project Using Composer

Use the composer create-project command to pull the laravel/laravel skeleton and install all dependencies. This command automatically executes Laravel's post-installation scripts.

composer create-project laravel/laravel my-app "12.*"

The framework registers Composer event hooks in src/Illuminate/Foundation/ComposerScripts.php. Specifically, the postInstall method (lines 22-28) triggers clearCompiled() to purge stale bootstrap caches immediately after package installation. This prevents "old config" bugs that occur when cached files persist across dependency changes.

Step 2: Verify PHP Version and Required Extensions

Before running any Artisan commands, verify that your PHP version matches the constraint defined in composer.json and that required extensions are enabled. The framework requires extensions such as openssl, pdo_mysql, mbstring, tokenizer, and xml.

In src/Illuminate/Foundation/Application.php (lines 181-190), the service container registers core features only when underlying extensions exist. Missing extensions cause runtime exceptions early in the bootstrapping process, before the application can handle errors gracefully.

Step 3: Configure the Environment File

Copy the environment template and generate a unique application encryption key:

cd my-app
cp .env.example .env
php artisan key:generate

The Application class loads the environment file via environmentFile() and environmentFilePath() methods (lines 728-740 in src/Illuminate/Foundation/Application.php). The KeyGenerateCommand (located in src/Illuminate/Foundation/Console/KeyGenerateCommand.php) writes a fresh APP_KEY to your .env file, which is required for signed cookies, encrypted data, and queued closures.

Step 4: Set Proper File Permissions

Laravel caches configuration, routes, and compiled services in storage/framework and bootstrap/cache. If these directories are not writable, the framework's clearCompiled() routine (called by Composer scripts) will silently fail.

sudo chown -R $USER:www-data storage bootstrap/cache
chmod -R 775 storage bootstrap/cache

The clearCompiled() method in src/Illuminate/Foundation/ComposerScripts.php (lines 95-115) attempts to delete cached config, services, and packages files. Without write permissions, stale caches persist and cause configuration mismatches.

Step 5: Start the Development Server (Optional)

Validate your installation by running the built-in development server:

php artisan serve

The ServeCommand (found in src/Illuminate/Foundation/Console/ServeCommand.php, lines 128-148) watches the .env file for changes and reloads the server when the environment is updated. This ensures you are testing the exact configuration you will use in production.

Step 6: Verify the Installation

Confirm the installation by checking the version and compiling the configuration cache:

php artisan --version
php artisan config:cache

The config:cache command compiles all configuration files into a single optimized file at bootstrap/cache/config.php. Running this immediately after installation validates that the environment can be bootstrapped without errors and that the cache directories have proper permissions.

Step 7: Version Control Best Practices

Commit the composer.lock file to ensure reproducible dependency versions across all environments, but keep .env out of version control. The lock file guarantees that every environment uses identical package versions, while the environment file contains sensitive credentials that should never be committed.

How Laravel's Composer Integration Works

Understanding the framework's internal Composer hooks helps diagnose installation issues. The ComposerScripts class handles three critical events:

1. postInstall: Clears compiled caches after initial installation
2. postUpdate: Purges caches after dependency updates
3. postAutoloadDump: Removes optimization files when the autoloader is regenerated

The clearCompiled() method instantiates a new Application instance with getcwd() and removes three specific cache files:

// src/Illuminate/Foundation/ComposerScripts.php – clear compiled files after install
protected static function clearCompiled()
{
    $laravel = new Application(getcwd());

    if (is_file($configPath = $laravel->getCachedConfigPath())) {
        @unlink($configPath);
    }

    if (is_file($servicesPath = $laravel->getCachedServicesPath())) {
        @unlink($servicesPath);
    }

    if (is_file($packagesPath = $laravel->getCachedPackagesPath())) {
        @unlink($packagesPath);
    }
}

During bootstrap, the LoadEnvironmentVariables class (located in src/Illuminate/Foundation/Bootstrap/LoadEnvironmentVariables.php) reads the file name from environmentFile() and resolves its full path via environmentFilePath():

// src/Illuminate/Foundation/Application.php – environment handling
public function environmentFile()
{
    return $this->environmentFile ?: '.env';
}

public function environmentFilePath()
{
    return $this->environmentPath().DIRECTORY_SEPARATOR.$this->environmentFile();
}

If you rename the environment file, you must update the bootstrapper or pass --env to Artisan commands.

Summary

• Use composer create-project to install Laravel and trigger automatic cache clearing via ComposerScripts.php
• Verify PHP extensions before installation to prevent bootstrap failures in Application.php
• Copy .env.example to .env and run key:generate to set up encryption keys required for security features
• Set 775 permissions on storage and bootstrap/cache to allow clearCompiled() to function correctly
• Run config:cache immediately after installation to validate the bootstrap process and optimize configuration loading
• Commit composer.lock but exclude .env from version control for reproducible, secure deployments
• Use php artisan serve for development, which watches .env changes via ServeCommand

Frequently Asked Questions

What is the correct command to install Composer Laravel for production?

Use composer create-project laravel/laravel project-name --no-dev to omit development dependencies. According to the framework's ComposerScripts.php, the installation still runs clearCompiled() to ensure no stale caches exist, but skips dev-only packages that should not deploy to production environments.

Why does Laravel require write permissions on the storage directory?

The framework writes compiled configuration, route caches, and service manifests to storage/framework and bootstrap/cache. The clearCompiled() method in ComposerScripts.php attempts to delete these files during installation and updates. Without write permissions, these operations fail silently, causing the application to load outdated cached configuration instead of fresh environment variables.

How does Laravel handle the environment file during installation?

The Application class defines environmentFile() and environmentFilePath() methods (lines 728-740 in src/Illuminate/Foundation/Application.php) to locate and load the .env file. The LoadEnvironmentVariables bootstrapper reads this file during the boot process. You must copy .env.example to .env before running any Artisan commands, as the framework attempts to load environment variables immediately upon instantiation.

What happens if I don't run php artisan key:generate after installing Laravel?

Without generating an APP_KEY, the framework cannot encrypt cookies, session data, or sensitive configuration values. The KeyGenerateCommand (in src/Illuminate/Foundation/Console/KeyGenerateCommand.php) generates a 32-character random string and writes it to the .env file. Missing or invalid keys cause runtime exceptions when the application attempts to use Laravel's encryption services.

{
  "mcpServers": {
    "instagit": {
      "command": "npx",
      "args": ["-y", "instagit@latest"]
    }
  }
}