Multiple Laravel Projects on the Same Server: Session Conflicts & Environment Overlap

Recently, I ran into a frustrating issue with user sessions getting invalidated across multiple Laravel projects hosted on the same server. Here’s how I discovered the root cause and fixed it.

🛠 Server Setup

• OS: CentOS 7
• Web Server: Apache
• PHP Handler: PHP-FPM
• Database: PostgreSQL
• PHP Version: 7.x
• Framework: Laravel

I had multiple Laravel projects deployed under different virtual hosts, all running on the same server.

❗ The Problem

After logging into one of the applications, users would suddenly get logged out — sometimes within seconds. Occasionally, login attempts failed with an error saying:

“These credentials do not match our records.”

This behavior was inconsistent and only occurred when more than one project was active at the same time.

🔍 Initial Findings

Upon inspecting browser cookies, I noticed:

• All applications were using the default laravel_session cookie.
• The domain was set to .xyz.com (a shared parent domain).

This meant sessions could conflict between apps, especially if the user accessed multiple apps under the same domain.

So, I updated each project’s config/session.php file to use unique session cookie names and distinct session_domain values.

// Example in config/session.php
'cookie' => env('SESSION_COOKIE', 'project1_session'),
'domain' => env('SESSION_DOMAIN', 'project1.xyz.com'),

Despite these changes, the logout issue persisted.

🧠 Deeper Root Cause: Shared PHP-FPM Pool & Uncached Config

After digging deeper, I realized this wasn’t just a cookie issue. The real culprit was how Laravel and PHP-FPM handle environment variables.

Laravel relies on the .env file for configuration — but if you don't run php artisan config:cache, Laravel will read .env on every request.

Here’s the catch:

• When multiple Laravel apps share the same PHP-FPM pool, the FPM worker processes may reuse the PHP runtime across projects.
• If config isn’t cached, and two requests hit different projects simultaneously, the .env of one project can bleed into the other.
• This causes unpredictable behavior: session mismatches, failed authentication, and even incorrect database connections.

✅ The Fix

To prevent .env files from being loaded dynamically on each request, I ran the following for each project:

php artisan config:cache

This caches the environment configuration into a PHP file, so Laravel no longer reads .env on every request. It ensures each project loads its own cached config, even if using the same FPM pool.

🔒 Best Practices for Multi-Laravel Hosting

If you’re running multiple Laravel projects on the same server, follow these to avoid environment conflicts:

1. Use Unique Session Settings
   In config/session.php, set a unique session_cookie and session_domain for each app.
2. Always Cache Configs
   Run php artisan config:cache after changes to .env or config files.
3. (Recommended) Use Separate PHP-FPM Pools
   For better isolation, configure separate FPM pools for each app in /etc/php-fpm.d/.
4. Example pool config (project1.conf):

[project1] listen = /run/php-fpm/project1.sock ...

1. And update Apache VirtualHost:

<FilesMatch \.php$>     SetHandler "proxy:unix:/run/php-fpm/project1.sock|fcgi://localhost/" </FilesMatch>

🎉 Conclusion

When multiple Laravel apps share a server, it’s easy to run into subtle bugs caused by shared sessions or overlapping environment configs. By:

• Customizing session settings
• Caching config files
• Using separate FPM pools

…you can avoid these conflicts entirely and keep your applications stable.

🧩 Your Input Matters

Have you encountered similar environment or session conflicts while hosting multiple Laravel projects on the same server? I’d be interested in hearing how you approached the issue — especially if you’ve used different strategies (like Docker, Nginx, or CI/CD optimizations).

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