/**
* @fn init_math_test
* @short Initializes the mathematical test to tell humans and machines apart.
*/
public static function init_math_test()
{
self::$first_operand = rand(0, 10);
self::$second_operand = rand(0, 10);
$_SESSION['antispam_math'] = array(self::$first_operand, self::$second_operand);
}