i try same hash in request header in (in1 and in2) but not work

this code i had problem with

<?php

include('info.php');

if( @$_GET['source'] == 1 ){
    highlight_file(__FILE__);
    die();
}

if( @$_GET['in1'] && @$_GET['in2'] )
{
    $input1 = $_GET['in1'];
    $input2 = $_GET['in2'];

if( $input1 !== $input2 && @hash("md5", $salt.$input1) === @hash("md5", $salt. $input2) ) 
    {
        echo $info;

    } else {

        echo "Sorry this value not valid.";
    }
} else{
    exit();
}

?>

i try same hash in request header but not work i also try different hash and same problem can any body

explain this line

if( $input1 !== $input2 && @hash("md5", $salt.$input1) === @hash("md5", $salt. $input2) )