Why is wordpress not installed under iis 7.0?

Question

IIS

Actually, windows server 2008 r2 sp1. IIS role installed with cgi. Installed RewriteModule, php 7.4, mariadb 10.4. The base is created, the site is created, index.php is registered as the initial page. phpinfo() works.

The first page opens. I press the "Go!" button. I open the second wordpress page - I enter the data of the created database. I click "Next". I get "500 - Internal Server Error. There is a problem with the requested resource; the resource cannot be displayed." The rights to the root directory c:\inetpub\wwwroot\wordpress\ for the groups "Everyone", "Authenticated", "Administrators", "Users", "system", "IIS_IURSR" and "TrustedInstaller" are fully set.

As far as I understand, wordpress installer can't create wp-config.php file in root directory? Or am I wrong? Where else to dig?

PS: "Great" people with their "Great" comments like "fuck iis, there is nginx/apache" please do not disturb.

PS: Enabled "Detailed error messages" on the error 500 page. Now instead of error 500 it appears:

PHP Fatal error:  Uncaught Error: Call to undefined function mysql_connect() in C:\inetpub\wwwroot\wordpress\wp-includes\wp-db.php:1688
Stack trace:
#0 C:\inetpub\wwwroot\wordpress\wp-admin\setup-config.php(310): wpdb->db_connect()
#1 {main}
  thrown in C:\inetpub\wwwroot\wordpress\wp-includes\wp-db.php on line 1688

Answer 1

c:\Program Files\PHP\php74\php.ini:

extension_dir = "c:\Program Files\PHP\php74\ext"
extension=mysqli

+ permissions to modify (recursively) the C:\inetpub\wwwroot\wordpress directory must be owned by the IURS group.