Create subdomains on the fly with info from database - php

Question

I am trying to achieve automatic subdomain creation. I have read a lot of tutorials including:
THIS
THIS
THIS
I understood the concept and I implemented it with success in the past for user profiles, but this is a different case and I am stuck.
What I want to do, is basically something like pen.io as functionality. A user creates a page with a password and then, that page name converts into a subdomain.
I thought of doing a function that runs on the index page of the main website and that one used afterwards in HTACCESS to have something like index.php?subdomain=test and that one to redirect to test.domain.tld
EDIT:
Here is the current implementation that works when clicking on a link, but it doesn't work when accessing the url directly from the browser:
Code used in view.php:
<?php
include('inc/config.php');
$url = filter_var($_GET['url'], FILTER_SANITIZE_STRING);
$conn = new mysqli($server, $username, $password, $database) or die ('Unable to execute query. '. mysqli_error($conn));
$query = "SELECT * FROM `pages` WHERE pageTitle = '$url'";
$result = $conn->query($query);
if($row = mysqli_fetch_array($result))
{
$title = $row['pageEditableTitle'];
$content = $row['pageContent'];
echo '<h5 class="mt-5"><mark>'.$title.'</mark></h5>
<p class="lead display-7">'.$content.'</p>';
} else {
echo '<br /><div class="alert alert-info" role="alert">Subdomain does not exist.</div>';
}
$conn->close();
?>
Code used in htaccess:
RewriteCond %{HTTP_HOST} ^(.*)\.domain\.tld
RewriteRule ^(.*)$ https://domain.tld/view.php?url=%1 [L,NC,QSA]
But this redirects www.domain.tld to domain.tld/view.php?url=www and not staying as www.domain.tld in the browser url

Answer 1

I presuppose that you setup a wildcard dns entry (access random.domain.tld to test it!). Then you have two options:
Correct your rewrite rules
Something like [aA-zZ] should be [a-zA-Z] and the RewriteRule should be only after the RewriteCond and not in front of it and two of them. And do you really want to force a - inside the subdomain with ([a-z0-9][-a-z0-9]+)? Maybe you should check this answer. Note: The www inside of your domain is a subdomain as well. So it would rewrite to sub.php?url=www
With the corrected rewriting random.domain.tld returns the content of random.domain.tld/sub.php?url=random. But at the moment your sub.php does not return content. Instead it returns a http redirect to the URL random.domain.tld. This means your sub.php produces an infinite loop on itself. Instead sub.php should only contain something like <?php echo $_SERVER['HTTP_HOST']; ?>.
Maybe you did not understand how URL rewriting works. Then read this answer for further explanation.
Update1
You corrected your code as follows:
RewriteCond %{HTTP_HOST} ^([a-zA-Z0-9]+)\.domain\.tld\.?(:80)?$ [NC]
RewriteRule ([a-zA-Z0-9]+) /view.php?url=$1
But it's still wrong. As I said you need to read and understand this answer. #JoachimIsaksson uses $1 and %1 in his 2nd example:
RewriteEngine on
RewriteCond %{HTTP_HOST} ^(.*)\.example\.com
RewriteRule ^(.*)$ /subdomains/%1/$1 [L,NC,QSA]
%1 is the subdomain catched through RewriteCond %{HTTP_HOST} ^(.*)\.domain\.com. And $1 is the path catched through RewriteRule ^(.*)$. You missed to use %1.
But your code can not work as you forced an unempty alphanummeric string by RewriteRule ([a-zA-Z0-9]+). But a path could contain more than that. For example a slash or question mark. And of course it could be empty as well.
And why did you add (:80)?? Do you think someone will access your domain with a specific port?
And why the last optional dot in tld\.??
At last you need to bring the flags into question. You used the NC flag. It means your rule is case-insensitive. So why do you use [a-zA-Z0-9]? As your rule is already case-insensitive it can be [a-z0-9]. And why don't you used the L and QSA flag? They are important.
Update2
Try this:
RewriteEngine on
RewriteCond %{HTTP_HOST} ^(.*)\.domain\.tld
RewriteRule .* view.php?url=%1 [L,NC,QSA]
Use PHP only
$_SERVER['HTTP_HOST'] contains your full domain. This answer explains how to extract the subdomain name:
$subdomain = array_shift((explode('.', $_SERVER['HTTP_HOST'])));
Now you are able to use your general index.php to switch between your general page or the users subdomain content:
$domain_parts = explode('.', $_SERVER['HTTP_HOST']);
// access without any subdomain (TLDs like "co.uk" would "need == 4")
if (count(domain_parts) == 3) {
$subdomain = "www";
}
else {
$subdomain = array_shift($domain_parts);
}
if ($subdomain == 'www') {
// general page
}
else {
// users page
}