how to get the previous page url in php

1basename($_SERVER['HTTP_REFERER']);

1$_SERVER['HTTP_REFERER']

1//This should be on the previous page
2session_start();
3$_SESSION["url"] = "the_url_of_page_we_want_to_get_back.php";
4
5//This should be on the current executing page
6session_start();
7$previous_page_url = $_SESSION["url"];