A website based on WordPress is inaccessible: 500 Internal server error, PHP Parse error: syntax error

Symptoms

• A WordPress-based website is not accessible with the following error in a browser:

  PLESK_INFO: 500 Internal server error

• One of the following error messages might appear in Plesk > Domains > example.com > Logs:

  CONFIG_TEXT: mod_fcgid: stderr: Error reading Wordfence Firewall config data, configuration file could be corrupted or inaccessible. Path: /var/www/vhosts/example.com/httpdocs/wp-content/wflogs/config.php

  CONFIG_TEXT: mod_fcgid: stderr: PHP Parse error: syntax error, unexpected 'class' (T_CLASS), expecting identifier (T_STRING) or variable (T_VARIABLE) or '{' or '$' in /var/www/vhosts/example.com/httpdocs/wp-content/plugins/sermon-manager-for-wordpress/sermons.php on line 53

  CONFIG_TEXT: mod_fcgid: stderr: PHP Parse error: syntax error, unexpected 'new' (T_NEW) in /var/www/vhosts/example.com/httpdocs/wp-content/themes/MissionWP22/option-tree/ot-loader.php on line 389

  CONFIG_TEXT: PHP Fatal error: Maximum execution time of 60 seconds exceeded in F:\Inetpub\vhosts\example.com\httpdocs\wp-includes\functions.php on line 1897

Cause

An incompatible PHP version is configured in the domain.

Resolution

1. Log in to Plesk GUI
2. Go to Domains > example.com > PHP Settings and change PHP according to the WordPress and Plugins requirements.
3. In case this issue persists, disable the WordPress plugin and contact WordPress Plugin developers to get support.

Additional Information

For the best experience, WordPress recommends PHP 7.4 or greater. For reference see WordPress requirements.

How to install/remove additional PHP versions provided by Plesk