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[FIXED] Error 502 Bad Gateway in Nginx with PHP-FPM

Read time: 4 min Updated: 2026-08-12
✨ Quick Answer

The 502 Bad Gateway error on Nginx web servers using PHP-FPM occurs when Nginx acts as a reverse proxy but fails to establish a socket connection with the PHP backend process. The error log at /var/log/nginx/error.log usually states: connect() to unix:/run/php/php8.2-fpm.sock failed (2: No such file or directory) or Connection refused.

Quick Diagnostics

Cause
php-fpm daemon service stopped or not started
Solution
Start PHP daemon: sudo systemctl start php-fpm (or php8.2-fpm)
Cause
Insufficient permissions on UNIX socket /var/run/php/php-fpm.sock
Solution
Change socket owner to www-data:www-data in /etc/php/fpm/pool.d/www.conf

The 502 Bad Gateway error on Nginx web servers using PHP-FPM occurs when Nginx acts as a reverse proxy but fails to establish a socket connection with the PHP backend process. The error log at /var/log/nginx/error.log usually states: connect() to unix:/run/php/php8.2-fpm.sock failed (2: No such file or directory) or Connection refused.

Quick Solution (1 Minute):

  1. Restart your active PHP-FPM service: sudo systemctl restart php8.2-fpm
  2. Ensure your Nginx fastcgi_pass directive matches your exact installed PHP socket version.

🚀 Step-by-Step Fixes

Step 1: Check PHP-FPM Daemon Status

Verify that PHP-FPM is active and running:

BASH 
sudo systemctl status php8.2-fpm

If status reports inactive or failed, enable and start it:

BASH 
sudo systemctl enable --now php8.2-fpm

Step 2: Verify Exact Socket (.sock) Path

Check the active socket location created by PHP:

BASH 
ls -la /run/php/

Expected output: php8.2-fpm.sock or php8.3-fpm.sock.

Open your Nginx site configuration file at /etc/nginx/sites-available/yourdomain.conf:

NGINX 
location ~ \.php$ {
    include snippets/fastcgi-php.conf;
    # MUST match your active .sock file path:
    fastcgi_pass unix:/run/php/php8.2-fpm.sock;
}

Step 3: Fix PHP-FPM Socket Permissions

If the .sock file exists but Nginx returns Permission denied in its logs:

Edit your PHP-FPM pool configuration:

BASH 
sudo nano /etc/php/8.2/fpm/pool.d/www.conf

Ensure the socket owner matches Nginx (www-data):

INI 
listen.owner = www-data
listen.group = www-data
listen.mode = 0660

Restart services:

BASH 
sudo systemctl restart php8.2-fpm
sudo systemctl restart nginx

Prevention Advice

Recommended security practices: