Domain’s PHP functional is not available: xxx() has been disabled for security reasons

Symptoms

• Cannot send mail via PHP script or cannot execute curl request via PHP script;

• The following error can be found in the domain's error log in Domains > example.com > Logs, alternatively, this error might be reflected instead of domain's content:

  Got error 'PHP message: PHP Fatal error: Uncaught Error: Call to undefined function mail() in /var/www/vhosts/example.com/httpdocs/test.php:3nStack trace:n#0 {main}n thrown in /var/www/vhosts/example.com/httpdocs/test.php on line 3'

Cause

PHP function xxx() is disabled in php.ini.

Resolution

Warning: These steps ONLY apply to PHP-FastCGI, they do NOT apply for PHP-FPM, because for FPM disabled_functions directives will get overwritten by the Global PHP Configuration.

Configuring disable_functions in Plesk interface for a particular domain:

1. Log into Plesk;

2. Go to Domains > example.com > PHP Settings, remove everything from disable_function section > OK:
   

   In case there is no disable_function section add the following line in Additional configuration directives field in Domains > example.com > PHP Settings > Additional directives to override main php.ini directives:

   disable_functions=""

   

Note: For the server-wide ways, check what PHP handler is enabled in Plesk > Home > Domains > example.com > PHP Settings . Let it be PHP 8.1.