How to make dynamic subdomains on app engine or openshift?

Question

PHP

On openshift there is access to .htaccess, on google app enigne - no, but here and there the domain is bound via CNAME (usually www.subdomain).
Judging by the documentation for GAE somehow - it works.
Tried advice from stackoverflow
RewriteEngine on
RewriteCond %{HTTP_HOST} ^(.*).domain.com$ [NC]
RewriteRule (.*) %1/$1 [L]
- doesn't work under these conditions.
First of all, the version of GAE php and routing to the subdomain for it are of interest.
Task: a user registers and is given a subdomain (trivial)

Answer 1

Judging by the documentation for GAE, there you need to add a subdomain named * in the control panel.
After that, all requests will come to the main web server, while a specific subdomain can be obtained from $_SERVER['HTTP_HOST'].

Answer 2

Not a domain, but a sub-domain, they are just under * in Apache, they are quietly controlled, for example, when redirecting from sub.domain to domain / sub. Or do you mean exactly these services?

Answer 3

"According to the documentation for GAE, there you need to add a subdomain named * in the control panel."
I'd love to, but I don't see that option.