Is it possible to pass php variable to ajax?

I try to make redirection after successful login.
In php if password and user match, then $_SESSION['loggedin'] = 1;
$ifloggedin = $_SESSION['loggedin'];

In ajax would need something like this

if($ifloggedin == 1) {
window.location = "login-success.php";
}

but seems something wrong.

Could someone explain or give link where I can read about the question?

You have to tell the page you want to use PHP:

if(<?php echo $ifloggedin ?> == 1) {
window.location = "login-success.php";
}

Thanks for answer, but seems I do not understand
At the moment I have such code

HTML Code:

---

hr.onreadystatechange = function() {
if(hr.readyState == 4 && hr.status == 200) {
var return_data = hr.responseText;
document.getElementById("status").innerHTML = return_data;
[B]window.location = "login-success.php";[/B]
}
}

---

It means in each case when visitor click login button, the visitor is redirected to login-success.php

What do i need to change/add to get visitor redirected only if php $variable==1; php is in other file....

Code:

---

<?php
  if ($variable == 1) {
?>

hr.onreadystatechange = function() {
if(hr.readyState == 4 && hr.status == 200) {
var return_data = hr.responseText;
document.getElementById("status").innerHTML = return_data;
window.location = "login-success.php";
}
}

<?php
}
?>

---