Website shows 500 Internal Server Error: mod_fcgid: error reading data from FastCGI server

Symptoms

• Webspace is inaccessible with the following error:

  CONFIG_TEXT: 500 Internal Server Error

• One of the following errors can be found in

  CONFIG_TEXT: /var/www/vhosts/example.com/logs/error_logs file:
  CONFIG_TEXT: /var/www/vhosts/example.com/logs/error_logs file:
  [error] [client ] Premature end of script headers: index.php, referer: http://example.com
  [warn] [client ] (104)Connection reset by peer: mod_fcgid: error
  reading data from FastCGI server, referer: http://example.com

  CONFIG_TEXT: AH01071: Got error 'PHP message: PHP Fatal error: Uncaught Error: Call to undefined function get_bloginfo() in /var/www/vhosts/example.com/httpdocs/wp-includes/class-wp-locale.php:231

  CONFIG_TEXT: (104)Connection reset by peer: mod_fcgid: error reading data from FastCGI server

• In /var/www/vhosts/example.com/logs/proxy_error_logs the following error can be seen:

  CONFIG_TEXT: [error] 28511#0: *7681 upstream prematurely closed connection while reading response header from upstream, client: , server: example.com, request: "POST /login HTTP/1.1", upstream: "http://203.0.113.2:7080/login", host: "example.com", referrer: "http://example.com"

Cause

Website code issues.

Resolution

Switch PHP handler from FastCGI to FPM:

1. Log in to Plesk
2. Go to Domains > example.com > PHP Settings
3. Select required PHP version and/or PHP handler from the drop-down list
4. Apply the changes

If the issue persists, contact the website developer