Serve new subdomains dynamically

I have a service example.com that needs to allow users to host a few files in their own subdomain userpage-userabc.example.com, similarly as does Github with userabc.github.io.

I currently use Apache, and each time I want to configure a new domain or subdomain, I have to create manually a new <VirtualHost>, restart the Apache server, etc. This is not possible here.

Example: if a visitor creates a new account userabc (added in a database), how to make that the userpage-userabc.example.com subdomain is available, and automatically serving files from /www/userabc/ or serving http://userpage-userabc.example.com/ with /www/main/index.php?user=userabc?

Note: *.example.com already has a wildcard A DNS-record to redirect to my server

What's a simple lightweight tool to do this "dynamic subdomain creation"? (I currently use Apache, PHP, Python, but I can use other tools).

Or is it possible with a single <VirtualHost> that catches all sudomains *.example.com and a RewriteRule including the subdomain?

As mentioned in a comment, here are references for Apache, there are multiple ways to do it: Dynamically Configured Mass Virtual Hosting, Dynamic mass virtual hosts with mod_rewrite.

The simplest solution I have found after a few more tests is: one single <VirtualHost>

<VirtualHost *:80>
  ServerName example.com
  ServerAlias *.example.com
  DocumentRoot /www/example
  <Directory />
    AllowOverride All
    Require all granted
  </Directory>
</VirtualHost>

with this wildcard ServerAlias.

With an .htaccess containing

RewriteEngine on
RewriteRule ^(.*)$ index.php [QSA,L]

we can then do all the routing for each user via PHP:

<?php
$host = $_SERVER['HTTP_HOST'];
$sname = $_SERVER['SERVER_NAME'];
// parse the subdomain of $host or $sname and deliver 
// the content accordingly (using the database)
?>

Benefit: it also works if the final user is using his own custom domain with a CNAME DNS record. Example:

www.userabc.com CNAME userpage-userabc.example.com

Then in the PHP, $host will here show www.userabc.com. If this custom domain information is somewhere in the database, we can serve the content accordingly, even if the user is using a custom domain.

Note: in the case for which users use their custom domain with CNAME, this is useful to determine which is the default VirtualHost to use when a request comes with a host which is not listed in the ServerName directives: Apache default VirtualHost.