I am reading a script but am stuck on understanding this:

```
$redirect = base64_decode($_REQUEST['redirect']);
header("Location:$redirect");exit;

```

because the redirect variable in REQUEST isn't defined anywhere in the script. Prior to this a POST form has been filled in, but there is NO mention of the redirect variable anywhere in the script so I am confused how it is not empty...

EDIT:

here's the form code below. btw like I said, the word 'redirect' doesn't appear ANYWHERE in the script, which is what is confusing me.

```
        <form name="login" action="{$baseurl}/login" method="post">
            {$lang12}
            <input type="text" name="username" />
            {$lang11}
            <input type="password" name="password" />
            <input type="submit" value="{$lang18}" />
            <div class="test"><a href="{$baseurl}/signup"><b>{$lang30}</b></a> - <a href="{$baseurl}/password">{$lang19}</a></div>
            <input type="hidden" name="authenticate" value="1" />
        </form>
        </div>

```

The $lang stuff is commonly appearing words from an array, e.g login, etc.