Plesk domain provides errors in PHP error logs: Unable to set php_value

Symptoms

• PHP-FPM directive like process_idle_timeout was specified for the domain in Plesk > Domains > example.com > PHP Settings > Additional configuration directives.

• Errors like below can be found in /var/log/plesk-phpXX-fpm/error.log (where XX is a PHP version used by the domain):

  Note: PHP directive name may vary.

  WARNING: [pool example.com] child 1549 said into stderr: "ERROR: Unable to set php_value 'pm.process_idle_timeout'"

Cause

Missing separator. pm variables require a special separator: [php-fpm-pool-settings].

Resolution

1. Log into Plesk.

2. Go to Domains > example.com > PHP Settings.

3. In the Additional configuration directives field add the separator [php-fpm-pool-settings] as shown on the screenshot below:
   

4. Apply changes.