How can I find previous visited url in PHP?

I believe what you want is called BREADCRUMBS.

What to use for navigation chain storage is actually up to you. You might even use

$_SERVER['HTTP_REFERER']

if you want, but that'd be unreliable as it's client-side. Usual way to store such chain is actual URI or session.

For example, you have such URI: http://www.example.com/post_manager/post

Then you can iterate through explode(

"/", $_SERVER["REQUEST_URI"]

) to get each step.

That's basic explanation to guide you to a right direction. You can google a lot of samples and snippets using keyword breadcrumbs.

On the topic of saving last visited location (the way to determine whether auser came from manager or homepage): you can use session's variables to do that. Here's an example:

This way you can set a variable on your homepage:

<?php
    session_start(); 
    $_SESSION['previous_location'] = 'homepage';
?>

And then you just access it from another page:

<?php
    $previous_location = $_SESSION['previous_location'];
?>

It's important to set session.save_path in your PHP configuration file or your sessions might get lost.