The mysqli extension allows you to access the functionality provided by MySQL 4.1 and above. More information about the MySQL Database server can be found at » http://www.mysql.com/
An overview of software available for using MySQL from PHP can be found at Overview
Documentation for MySQL can be found at » http://dev.mysql.com/doc/.
Parts of this documentation included from MySQL manual with permissions of Oracle Corporation.
Examples use either the » world or » sakila database, which are freely available.