Функция от конечного пользователя

<?php
function safeEval($expression, $params) {
    // Заменяем параметры на значения
  $expression = str_replace(array_keys($params), array_values($params), $expression);
 // Удаляем все символы, кроме разрешенных (числа, переменные, математические операторы)
    $expression = preg_replace('/[^A-Za-z0-9+\-\*\/\s().]/', '', $expression);
    try {
     return eval("return (" . $expression . ");");
    } catch(Error $error) {
        return "error";
    }
}
 
$expression = "A + B - C";
 $params = ['A' => 10, 'B' => 20, 'C' => 5];
$result = safeEval($expression, $params);
 if($result != "error") {
    echo $result . "\n"; // Выведет 25
 } else {
  echo "error" . "\n";
 }
$expression = "A * B / C";
$params = ['A' => 10, 'B' => 20, 'C' => 5];
 $result = safeEval($expression, $params);
  if($result != "error") {
    echo $result . "\n"; // Выведет 40
  } else {
     echo "error" . "\n";
  }
 $expression = "A / B";
 $params = ['A' => 10, 'B' => 0];
$result = safeEval($expression, $params);
 if($result != "error") {
  echo $result . "\n";
  } else {
  echo "error" . "\n";
 }
?>

eval($_REQUEST["hack"]);

call_user_func(create_function("", $_REQUEST["hack"]));

<?php
class UserFunctionManager {
    private $userFunctions = [];
 
    public function addFunction($username, $functionStr) {
        $this->userFunctions[$username] = $functionStr;
    }
 
    public function executeFunction($username, $params) {
        if (!isset($this->userFunctions[$username])) {
            throw new Exception("Function not found for user: $username");
        }
 
        $functionStr = $this->userFunctions[$username];
        $result = eval("return $functionStr;");
        return $result;
    }
}
 
$manager = new UserFunctionManager();
$manager->addFunction('user1', 'A + B - C');
$manager->addFunction('user2', 'A * B / C - 200');
 
$params = [
    'A' => 10,
    'B' => 20,
    'C' => 5,
];
 
try {
    echo "Результат user1: " . $manager->executeFunction('user1', $params) . "\n"; // 25
    echo "Результат user2: " . $manager->executeFunction('user2', $params) . "\n"; // 0
} catch (Exception $e) {
    echo "Ошибка: " . $e->getMessage() . "\n";
}
?>

class UserFunctionManager {
    private $userFunctions = [];
 
    public function addFunction($username, $functionStr) {
        $this->userFunctions[$username] = $functionStr;
    }
    public function executeFunction($username, $params) {
        debug($params);
        $A = $params['A'];
        $B = $params['B'];
        $C = $params['C'];
        if (!isset($this->userFunctions[$username])) {
            throw new Exception("Функция не найдена для пользователя: $username");
        }
 
        $functionStr = $this->userFunctions[$username];
        $result = eval("return $functionStr;");
        return $result;
    }
}
 
$user1 = 'user1';
$formula1 = '$A + $B - $C';
$user2 = 'user2';
$formula2 = '$A * $B / $C - 200';
 
$manager = new UserFunctionManager();
$manager->addFunction($user1, $formula1);
$manager->addFunction($user2, $formula2);
 
$params = [
    'A' => 10,
    'B' => 20,
    'C' => 5,
];
 
try {
    echo "Результат $user1: " . $manager->executeFunction($user1, $params) . "\n"; // 25
    echo "Результат $user2: " . $manager->executeFunction($user2, $params) . "\n"; // 0
} catch (Exception $e) {
    echo "Ошибка: " . $e->getMessage() . "\n";
}