I'm installing Zenphoto for the first time by following the instruction here:
https://www.zenphoto.org/news/installation-and-upgrading/

When I visit my website, the setup won't run. Apache's log displays the following:

[Thu Feb 08 11:09:53.860794 2024] [php:warn] [pid 1137] [client 202.186.128.89:10873] PHP Warning: filemtime(): stat failed for /var/www/example.com/zp-data/zenphoto.cfg.php in /var/www/example.com/zp-core/setup/index.php on line 115
[Thu Feb 08 11:09:53.861088 2024] [php:warn] [pid 1137] [client 202.186.128.89:10873] PHP Warning: fileperms(): stat failed for /var/www/example.com/zp-data/zenphoto.cfg.php in /var/www/example.com/zp-core/setup/class-setup.php on line 686
[Thu Feb 08 11:09:53.861407 2024] [php:warn] [pid 1137] [client 202.186.128.89:10873] PHP Warning: Undefined variable $selected_database in /var/www/example.com/zp-core/setup/index.php on line 345
[Thu Feb 08 11:09:53.861550 2024] [php:error] [pid 1137] [client 202.186.128.89:10873] PHP Fatal error: Uncaught Error: Class "dbBase" not found in /var/www/example.com/zp-core/setup/index.php:370\nStack trace:\n#0 {main}\n thrown in /var/www/example.com/zp-core/setup/index.php on line 370

Help is greatly appreciated.

Your file/folder permissions are not correct or run with the wrong server user so the config file cannot be loaded: https://www.zenphoto.org/news/permissions-for-zenphoto-files-and-folders/

You may have to ask your host about that.

Thanks, it works now. I had set the files and folders' owner to the wrong user, it should be 'www-data'.