如何使用CURL和PHP访问远程数据库？

Question

I have this homework problem:

Use CURL to implement the following:

For each company web site, create a php web app/link that shows a list of users from your own company.
Assume we have a group of 3 (Company A, Company B and Company C). Thus, we have
list_of_users_A that is stored in a database A in Company A host system
list_of_users_B that is stored in a database B in Company B host system
list_of_users_C that is stored in a database C in Company C host system
Each company web site needs to create a web link that shows list_of_users from all companies. You can access your local list_of_user via normal php database call, but you need to access remote company's database via CURL calls.

I understand how to access a webpage and get the information using CURL, but I've been googling and don't understand how to access a remote database using CURL.

I can access a remote database using mysqli_connect, but that's not using CURL is it?

Thanks!