PHP filter_input not working

Question

I have a PHP script that shows some server variables, the code is as following :

<?php
$FILTEREDHOST = filter_input(INPUT_SERVER,'HTTP_HOST');
$FILTEREDSELF = filter_input(INPUT_SERVER,'PHP_SELF');

$SERVERHOST = $_SERVER['HTTP_HOST'];
$SERVERSELF = $_SERVER['PHP_SELF'];

var_dump($FILTEREDHOST);
echo "</br>";
var_dump($FILTEREDSELF);
echo "</br>";
var_dump($SERVERHOST);
echo "</br>";
var_dump($SERVERSELF);

The result I get is :

NULL
string(9) "/test.php"
string(17) "www.mysite.com"
string(9) "/test.php" 

Why $FILTEREDHOST is returning NULL ?

My PHP version is 5.5.16

Answer 1

HTTP_HOST is not set if the browser didn't send it.

'HTTP_HOST' Contents of the Host: header from the current request, if there is one.

http://php.net/manual/en/reserved.variables.server.php