How To Build My Own Validator: FILTER_VALIDATE_STRING ?

developer_web · 2021-10-28T15:26:05+00:00

Folks, Subject today are the VALIDATORS in the function filter_input(). So far, we got these built-into php: A. filter_input(INPUT_POST,"$input",FILTER_VALI...

How To Build My Own Validator: FILTER_VALIDATE_STRING ?

developer_web

ginerjm

Here, glad to sort of teach you something new:
https://www.w3schools.com/php/filter_callback.asp
That should drop the 3 smiles off your 3 heads.

ginerjm

I have no interest in whatever it is you are doing. And no interest in anything w3schools has to say.

developer_web

ginerjm

Here, glad to sort of teach you something new:
https://www.w3schools.com/php/filter_callback.asp
That should drop the 3 smiles off your 3 heads.

Ok. I understand my mistake ...


$input = '123';

if(!filter_input(INPUT_POST,"$input",FILTER_VALIDATE_STRING4))

developer_web

NogDog

I tried the CALLBACK as suggested.
But it ain't working.

<form method="POST" name="textfield" id="textfield" action="" required>
<label for="name">Name:</label><br>
<input type="text" name="name" id="name" maxlength="255" size="25">
<br>
<button type="reset">Reset!</button>
<br>
<button type="submit" name="submit" id="submit">Submit!</button><br>
</form>

<?php
if($_SERVER['REQUEST_METHOD']==='POST')
{
	$name = $_POST['name'];
	
function FILTER_VALIDATE_STRING6($data)
{
	if(is_string($data))
	{
		$value = TRUE;
	}
	else
	{
		$value = FALSE;		
	}
	GLOBAL $value;
	return $value;
}

echo FILTER_VALIDATE_STRING6($name);
if(!filter_input(INPUT_POST,"name",FILTER_CALLBACK,
"FILTER_VALIDATE_STRING6"))
{
	die("Enter a valid STRING!");
}
}
?>

Warning: filter_input(): First argument is expected to be a valid callback in C:\xampp\htdocs\TEST.php on line 189
Enter a valid STRING!

NogDog

I have never used filter_input() in over 20 years of PHP coding, and see no reason to start using it now. If you are able to write a function that validates whatever it is you want to validate, just call it directly -- I see zero reason to embed it within another function.

developer_web

NogDog

Ok NogDog.
But you use filter_var() frequently and so let's try it with that. It's all about me getting to learn to use the CALLBACK function as it's new to me. Ok ?
Here's my attempt ...

<form method="POST" name="textfield" id="textfield" action="" required>
<label for="name">Name:</label><br>
<input type="text" name="name" id="name" maxlength="255" size="25">
<br>
<button type="reset">Reset!</button>
<br>
<button type="submit" name="submit" id="submit">Submit!</button><br>
</form>

<?php

if($_SERVER['REQUEST_METHOD']==='POST')
{
	$name = $_POST['name'];
	
function FILTER_VALIDATE_STRING6($data)
{
	if(is_string($data))
	{
		$value = TRUE;
	}
	else
	{
		$value = FALSE;		
	}
	GLOBAL $value;
	return $value;
}

echo FILTER_VALIDATE_STRING6($name);

if(!filter_var($name,FILTER_CALLBACK,
"FILTER_VALIDATE_STRING6"))
{
	die("Enter a valid STRING!");
}
}
?>

Warning: filter_var(): First argument is expected to be a valid callback in C:\xampp\htdocs\TEST.php on line ...

NogDog

developer_web But you use filter_var() frequently

Nope, don't use it, either.

NogDog

$name doesn't exist, but $_POST['name'] might.

developer_web

NogDog

But $name does exist. Look:

if($_SERVER['REQUEST_METHOD']==='POST')
{
	$name = $_POST['name'];

Anyway, did not make any difference. Still the error.

if($_SERVER['REQUEST_METHOD']==='POST')
{
	$name = $_POST['name'];
	
function FILTER_VALIDATE_STRING6($data)
{
	if(is_string($data))
	{
		$value = TRUE;
	}
	else
	{
		$value = FALSE;		
	}
	GLOBAL $value;
	return $value;
}

echo FILTER_VALIDATE_STRING6($name);

if(!filter_var($_POST['name'],FILTER_CALLBACK,
"FILTER_VALIDATE_STRING6"))
{
	die("Enter a valid STRING!");
}
}
?>

Warning: filter_var(): First argument is expected to be a valid callback in C:\xampp\htdocs\TEST.php on line ...

NogDog

That 3rd parameter to filter_var() needs to be an array. If we clean things up a bunch and try to K.I.S.S. (keep it simple, stupid), you could do:

<?php
// simulate POST request for this test:
$_SERVER['REQUEST_METHOD'] = 'POST';
$_POST['name'] = 'test';

if ($_SERVER['REQUEST_METHOD'] === 'POST') {
  if(!filter_var($_POST['name'], FILTER_CALLBACK, ["options" => "my_is_string"])) {
      die("Enter a valid STRING!");
  }
  echo "'{$_POST['name']}' is a string.";
}

// ridiculously redundant function wrapper:
function my_is_string($data)
{
  return is_string($data);
}

NogDog

PS: Note that everything in the $_POST array will be of type string, so this is all actually completely unnecessary for this specific test.

developer_web

NogDog

Mmm. But is not this true for $_GET also ?
So, show me a simple example where it won't become unnecessary then to use all this.

I also notice on tutorials that the 3rd param of filter_input() is also an array.

if(!filter__input(INPUT_POST,"name", FILTER_CALLBACK, ["options" => "my_is_string"])) {
      die("Enter a valid STRING!");
  }

But on both occassions (filter_var(), filter_input()), we see on tutorial examples, the 3rd param with the array:
FILTER_CALLBACK, ["options" => "my_is_string"])

But we do not see the array getting defined anywhere before the ''calling'' it line. How so ?

NogDog

developer_web do not see the array getting defined

Because in PHP version 7+ you can use the ["key" => "value", "key2" => "value2"] syntax to define an array, so it's defining it right when it calls the function.

developer_web this true for $_GET also ?

Yes

chavsur

i was also looking for the same, thanks for answers.. .