Website shows "An unexpected database error occurred. Please try again later." message

Symptoms

• A PHP forum application shows an error similar to the following after a content migration to a new server:

  An unexpected database error occurred. Please try again later.

• SELinux errors can be found in /var/log/plesk/panel.log:

  SELinux is preventing /opt/plesk/php/8.2/sbin/php-fpm from connect to access on the unix_stream_socket /var/lib/mysql/mysql.sock. For complete SELinux messages run: sealert -l 4351bc75-4efb-407b-8cbb-aa0878113737

• There are messages referring to denied permissions in Domains > example.com > Dashboard > Logs, but when checked, CHMOD permissions are correct. For example:

  An exception occurred: [XF\Db\Exception] Permission denied in src/XF/Db/Mysqli/Adapter.php

• Disabling SELinux enforcing makes the PHP forum work again.

  # setenforce 0

Cause

SELinux is preventing PHP-FPM access to the MySQL socket.

Resolution

Create the SELinux rule to allow the PHP-FPM services to connect to the MySQL socket:

1. Connect to the server via SSH

2. Review the SELinux audit log for more issues

   # ausearch -m avc -ts recent

3. Generate new policy from the audit log

   # ausearch -m avc -c php-fpm | audit2allow -M php-fpm

4. Activate the policy

   # semodule -i php-fpm.pp

5. Verify

   # semodule -l | grep php-fpm