header（）自动移动我

Question

AJAX:

$.ajax(
                {
                    type: "POST",
                    url: "validate.php",
                    data: {password: password},
                    success:
                    function(data)
                    {
                        if(data == "1")
                        {
                            alert("password c.");
                            var header = "<?php header('Location: administration.php'); ?>";
                            alert(header);
                        }
                        else
                        {
                            alert("password - inc.");
                        }
                    }
                });

validate.php:

<?php
if(isset($_POST["password"]))
{
    $password = $_POST["password"];

    if($password == "0000")
    {
        echo("1");
    }
    else
    {
        echo("0");
    }
}

?>

If I want to back from administration.php to index.php, function header() moves me to the index automatically. Why? How do I make a move only when my password is entered? So the password has to be entered even if I move from administration.php to index.php.