How to get current webpage name and echo with some modification - php

Question

I am trying something strange with code i just want to know weather it is possible to perform a php code like this one
<?php
$cururl= ucfirst(pathinfo($_SERVER['PHP_SELF'], PATHINFO_FILENAME));
$nexurlw = $cururl-1;
echo "$nexurlw";
?>
I have a problem in this code. My current page url is 30.php and i have a button on page "go to previous page" i want to change its url 29.php with the help of this function.
But this function echo 30 every time.

Answer 1

Try this :
$cururl = ucfirst(pathinfo($_SERVER['PHP_SELF'], PATHINFO_FILENAME));
$intUrl = ((int) $cururl) - 1;
$nexurlw = (string) $intUrl.'.php';
echo "$nexurlw";

Answer 2

Even if it happens to be true in your case (because that's the default in a raw PHP installation) there's often no direct mapping between URL locations and filesystem objects (files / directories). For instance, this question's URL is
https://stackoverflow.com/questions/68504314/how-to-get-current-webpage-name-and-echo-with-some-modification but the Stack Overflow server does not have a directory called 68504314 anywhere on its disk.
You want to build a URL from another URL, thus there's no even any benefit in having the filesystem involved, you can just gather the information about current URL from $_SERVER['REQUEST_URI']. E.g.:
$previous_page_url = null;
if (preg_match('#/blah/(\d+)\.php#', $_SERVER['REQUEST_URI'], $matches)) {
$current_page_number = (int)$matches[1];
if ($current_page_number > 1) {
$previous_page_url = sprintf('/blah/%d.php', $current_page_number - 1);
}
}