How to install Bitrix on a subdomain?

Question

PHP

Good day, please tell me how to put Bitrix on a subdomain?
The essence of the problem:
I uploaded a backup and restore.php to the root of the subdomain, a subdomain of the site.site.ru type. I
call restore.php , and then the following error pops up
Error: this script must be started from Web Server's DOCUMENT ROOT
Next, I create the test.php file with the following content

[<?=$_SERVER['REQUEST_URI']?>],[<?=$_SERVER['DOCUMENT_ROOT']?>]

Answer:
[/test.php],[/var/www/u0090692/data/www/alpham.ru]

Answer 1

Looks like a server configuration error. Bitrix is ​​placed in the subdomain in the same way as on the main address.