Can i get this straight in php filters (FILTER_REQUIRE_ARRAY, FILTER_REQUIRE_SCALAR , FILTER_FORCE_ARRAY )

Question

3 php constants i am not sure what they do

1. FILTER_REQUIRE_ARRAY

The name says it all I can agree no more but there is a function called
<em>filter_var/input_array()</em> which works in similar fashion; 
I've seen examples where recursive validation is required but 
not all element in the array are arrays some items are just scalar value 

FILTER_REQUIRE_SCALAR

    <?php 
        $x = 5;
        $y = [1, 2, 3];

        var_dump(filter_var($x,FILTER_REQUIRE_SCALAR));
        var_dump(filter_var($y,FILTER_REQUIRE_SCALAR));
    ?>

Consider The prev code that produces

bool(false)
bool(false)
as use can see $x is indeed Scalar

FILTER_FORCE_ARRAY

Always returns an array This is all the documentation i found about this in phpDoc give me an example about this please

Answer 1

FILTER_REQUIRE_ARRAY:

<?php

$arr = array(1,2,3,4,5);
$a = 3;
$result = filter_var( $arr,FILTER_VALIDATE_INT, FILTER_REQUIRE_ARRAY);
var_dump($result); 

// output:
array (size=5)
  0 => int 1
  1 => int 2
  2 => int 3
  3 => int 4
  4 => int 5

$result = filter_var( $a,FILTER_VALIDATE_INT, FILTER_REQUIRE_ARRAY);
var_dump($result); // boolean false

In this snippet, if one expects the input to be an array, by using the option FILTER_REQUIRE_ARRAY, it helps to avoid validating input containing a scalar value instead of an array.

filter_var_array() would not work in with the data in this example because it expects that the data is as follows:

An array with string keys containing the data to filter. (see Manual)

FILTER_REQUIRE_SCALAR:

<?php

$arr = array(1,2,3,4,5);
$a = 3;
$result = filter_var( $arr,FILTER_VALIDATE_INT, FILTER_REQUIRE_SCALAR);
var_dump($result); // boolean false

$result = filter_var( $a,FILTER_VALIDATE_INT, FILTER_REQUIRE_SCALAR);
var_dump($result); // int 3

In the preceding code, if one expects the input to be a scalar, by using the option FILTER_REQUIRE_SCALAR, it is useful in detecting if the input contains an array of info instead of the expected scalar value.

Here is a simple example that uses FILTER_FORCE_ARRAY:

<?php

$num = "1";
$result = filter_var( $num,FILTER_VALIDATE_INT,FILTER_FORCE_ARRAY);
var_dump($result);

// output:
array (size=1)
  0 => int 1

If the flag FILTER_FORCE_ARRAY were not present, then $result would be int 1