I've got a MySQL database which contains users and their passwords. I have
a PHP script that allows me to add new users and passwords to the database
via a web form.

What is the syntax to grant those newly added users select, insert, delete,
and update access to the database? I know how to do this from the command
line, but I want the PHP script to do it automatically when a user is added
to the database.

In other words, the users that I am adding will have the ability to query,
update, and delete themselves from the database as well as other users.