PHP Header redirects falling through if statements

Question

I have some code to log how many password attempts have been tried that looks like this:

<?php
/* Access denied */
$_SESSION['error'] = "invalidlogin";

if (isset($_SESSION['tries']))
{
    if ($_SESSION['tries'] == 5)
    {
        //TODO: Redirect somewhere nicer and more descriptive
        header("location:/index.php");
    }
    else
    {
        $_SESSION['tries']++;   
    }
}
else
{
    $_SESSION['tries'] = 0; 
}

header("location:/login.php");
?>

I know it is counting up to five and then stopping cuz I tested it by echoing $_SESSION['error'] on login.php

PHP never redirects when it hits

header("location:/index.php");

But it always keeps going and then redirects to

header("location:/login.php");

How can I get PHP to redirect as soon as it hits the index.php redirect?

Do I just set a boolean after the index.php redirect and check it on the login.php redirect?

EDIT: To clarify, I have already defined a session_start(); don't worry about that.

Answer 1

header("location:/index.php");
exit();

Answer 2

A redirect only takes effect AFTER it's been sent to the client's browser and the browser initiates a new request (which terminates the current request). Simply calling header() doesn't initiate the redirect - your script will keep running until it exits normally, the connection is closed and the webserver shuts down the script, or you explicitly terminate execution.

if you want a redirect header to take effect immediately, you need to terminate the script, which causes a flush of any pending output (including the redirect header):

header("Location: ...");
exit();