Very Good idea.
Ticket #2582 recorded

(notice that community version will be soewhat different from yours, for instance because we use camelCase for naming conventions)

For information, we started implementing Request Handler, but not as singleton : it is an abstract class will all static functions.
We also use camelCase naming.
We start using is for new needs and will try and find time to replace all direct call to $_REQUEST with call to functions of this class.
Thnaks for the idea.

Here is first version :

abstract class RequestHandler {

  public static function getValue($code,$required=false,$default=null) {
    if (isset($_REQUEST[$code])) {
      return $_REQUEST[$code];
    } else {
      if ($required) {
        throwError("parameter '$code' not found in Request");
        exit;
      } else {
        return $default;
      }  
    }
  }
  
  public static function getClass($code,$required=false,$default=null) {
    $val=self::getValue($code,$required,$default);
    if ($val==$default) return $val;
    return Security::checkValidClass($val);
  }
  
  public static function getId($code,$required=false,$default=null) {
    $val=self::getValue($code,$required,$default);
    if ($val==$default) return $val;
    return Security::checkValidId($val);
  }
  
  public static function getNumeric($code,$required=false,$default=null) {
    $val=self::getValue($code,$required,$default);
    if ($val==$default) return $val;
    return Security::checkValidNumeric($val);
  }
  
  public static function getAlphanumeric($code,$required=false,$default=null) {
    $val=self::getValue($code,$required,$default);
    if ($val==$default) return $val;
    return Security::checkValidAlphanumeric($val);
  }
  
  public static function getDatetime($code,$required=false,$default=null) {
    $val=self::getValue($code,$required,$default);
    if ($val==$default) return $val;
    return Security::checkValidDateTime($val);
  }
  
  public static function getYear($code,$required=false,$default=null) {
    $val=self::getValue($code,$required,$default);
    if ($val==$default) return $val;
    return Security::checkValidYear($val);
  }
  
  public static function getMonth($code,$required=false,$default=null) {
    $val=self::getValue($code,$required,$default);
    if ($val==$default) return $val;
    return Security::checkValidMonth($val);
  }
  public static function getExpected($code,$expectedList) {
    $val=self::getValue($code,true,null);
    if (in_array($val, $expectedList)) {
      return $val;
    } else {
      throwError("parameter $code='$val' has an unexpected value");
      exit;
    }
  }
  
}

Ok. I prefer singleton, but the result is quite the same.
At the moment I have used RequestHandler in a large amount of modules; if you believe that this can help you, I can send my code to you.
Best regards.

Hi,
Thanks for your proposale.
Yes, please snd your code, I'll have a look at least and check if I can use it (or part of it).

Ok,
in attachment a version of getSingleData.php based on RequestHandler class.
I had to add a method to the class
public static function isRequestSet($code) {
return isset($_REQUEST[$code]);
}

Let me know if this kind of cooperation can be useful. If so, I'll send new modules time by time.
Best regards

I took your work into account.
Thanks !

I notice now that you used a different signature in RequestHandler in order to distinguish between optional and mandatory parameters in Request.
I used $default = 'none' so missing argument can be easily detected to assume that parameter is mandatory.
If you really prefer your approach, you should use $required=true as it refers to the condition of accessing $_REQUEST element with no previous isset test.
This is, for example, what happened in original getSingleElement.php code; using my version and $required=false, exception will be avoided, but I'm not sure that you really want this.
Let me know before I proceed supplying you other code.
Best Regards

I used $default = 'none' so missing argument can be easily detected to assume that parameter is mandatory.

I prefer the explicit $required parameter, because 'none' is a string and could be a possible default value.

If you really prefer your approach, you should use $required=true as it refers to the condition of accessing $_REQUEST element with no previous isset test.

You're right. I prefered the default to false because it would not raise "Hack Detected" when not necessary. But in the other hand it will not when nedded...
I think best is to set signature as
getValue($code,$required,$default=null)
with no default value for $required.
This way, we'll have to think about need for a required Request attribute or not.
I'll keep existing signature until sure all calls have been upgraded...