Question /vhosts/default doesn't behave as a virtual host

[Dacey]

The request : http://my_ip/script.php opens/downloads the php file /vhosts/default/htdocs/script.php instead of executing it ! Obviously /vhosts/default is not considered as a virtual host. It seems I need to modify the configuration somewhere, but I don't known where : Plesk, Apache, nginx ?

 

[IgorG]

First of all try to fix it with:

# plesk repair web

and check that you have enabled correct PHP handler for this domain. Try to re-add it.

 

[Dacey]

Thank you.

check that you have enabled correct PHP handler for this domain

But there is no domain, that's where the problem lies.
Behind my IP, I have 3 domains where http://my_domain/script.php works perfectly.
My problem is to execute script.php by default, at http://my_ip/script.php