Description

When using PHP 8+ with the function "disk_free_space" disabled, this throws the following error:

Exception - Call to undefined function core\session\disk_free_space()

Cause

The error handling of the "@" character has changed with PHP 8 and PHP 8.1. If functions are addressed that are deactivated on the server side, a fatal error occurs even if this function is provided with an "@".
 
In this case, it happens in the following file:

/lib/classes/session/file.php:67

$freespace = @disk_free_space($this->sessiondir);

Solution

in PHP 8+ we must check the function with "function_exists" implicit and not use "@", because in shared hosting some php functions could be disabled.

Change the mentioned line code with:

$freespace = function_exists('disk_free_space') ? disk_free_space($this->sessiondir) : false;

Github Compare for pull-request: https://github.com/moodle/moodle/compare/main...fedealvz:moodle:main