PHP Header Exceptions - php

Question

I have a seperate navigator.php included on top of every page that I have for public.And it has a login form.If users have an account,they can login and be sent to the current page that they are at.
I pass the current URL adress to a hidden input as it's value.And post it to giris.php(login).Then redirecting the user with Header.
But when it comes to register.php(when no sessions were set);Im trying to login there and it still sends me back to the register.php.But SESSION is being set.Thats where I need an exception and want to send user to the index.php through register.php.
navigator.php
<div id="top">
<ul class="topnav" id="myTopnav">
<li>Anasayfa</li>
<li>İletişim</li>
<li>Hakkımızda</li>
<?php
if (isset($_SESSION["giris"]))
{
echo '<li>Panel</li>
<li>Çıkış Yap</li>';
}
else
{
$url= $_SERVER["REQUEST_URI"];
echo '<li>Kayıt Ol</li>
<li id="log">
<form method="post" action="giris.php"><div id="login">
<input type="hidden" name="location" value="'.$url.'">
<input type="text" name="username" placeholder="Kullanıcı Adı" class="loginField" required>
<input type="password" name="password" placeholder="Şifre" class="loginField" required>
<input type="submit" name="login" value="Giriş" id="logBut">
</form>
</li>';
}
?>
<li class="icon">
☰</li>
</ul>
</div>
<div id="banner">
<div id="title">
<h1>Topluluk Bloğu</h1>
<br/>
<h5>Community Blog</h5>
<br/>
<?php if(isset($_SESSION["giris"])){echo '<p id="username">Hoşgeldin '.$_SESSION["kullanici"].'</p>'; }?>
</div>
</div>
giris.php
<?php
session_start();
ob_start();
include 'func/constr.php';
if(isset($_POST["login"]))
{
$kullanici = $_POST['username'];
$password = $_POST['password'];
$URL = $_POST["location"];
$query = mysqli_query($connect,"SELECT * FROM kullanicilar where kullanici_adi='$kullanici' and sifre='$password'");
$count = mysqli_num_rows($query);
if ($count == 1)
{
$_SESSION["giris"] = true;
$_SESSION["kullanici"] = $kullanici;
$_SESSION["sifre"] = $password;
header("Location:$URL");
}
else
{
$invalid = "Kullanıcı adı ya da şifre yanlış";
$_SESSION["invalid"] = $invalid;
header("Location:index.php");
}
}
ob_end_flush();
?>

Answer 1

try this but not tested, if your other code is ok and redirect problem then
header("Location:$URL");
to
header('Location: ' . $URL);