Get Facebook URL inside app

Question

I'm using this code to get the current page URL:

<?php
$url="http://".$_SERVER['HTTP_HOST'].$_SERVER['REQUEST_URI'];
echo $url;
?>

On the website, the result is like you see in the image below.

But when I use this inside the Facebook app it gives me the same result instead of giving me the app URL, as you can see in the image below.

How do I get the Facebook app URL inside the app page?

Answer 1

Client-side

The more obvious method is to use JavaScript, since your Web server has no awareness of the <frame> itself. But unless you're accessing a frame whose parent frame is hosted on the same domain, the child cannot access (or manipulate) the parent frame. Allowing you to do so would violate JavaScript's same-origin policy.

If they're on the same domain, you can find the URL like so:

window.parent.location // Location object
window.parent.location.href // "http://..."

A similar question's answer recommends using document.referrer to see whether the request is from Facebook; but that doesn't tell you the full URL. So it's not useful if you had multiple app IDs pointing to the same Facebook app. In that case, add a query string parameter to the Facebook Page Tab URL and base your app's content on that query string parameter.

Server-side (PHP)

For example, in Facebook, add a query string ?referrer=appid123 to the Page Tab URL. In PHP, you can check against the query string parameter like so:

if($_GET['referrer'] == 'appid123'){
    // Do something for this visitor, who has come via my Facebook app
}

Answer 2

i have solved it by using this code to check if the user whose viewing this website is inside facebook app page or inside the website it self.

<?php 

$is_fb =   ( $_SERVER["SERVER_PORT"] !== 80 ) ? "".$_SERVER["SERVER_PORT"] : "";

if ($is_fb == 80) {
    /// The User is inside the website
    $InsideFacebook = '0';
}else{
    /// The User Inside Facebook app page
    $InsideFacebook = '1';
}

?>

This code is doing the following

If the user inside website http://my-website.com/website/ the port will be 80

If the user is on Facebook App Page the port will be different than 80