One of the best features of PHP is how easily it interacts with MySQL. This allows you to store information in a database for your website to access and then create dynamic content. In order to do this you need to be able to read and write to the MySQL database from your PHP based website.
You can connect to your database from a PHP file with the following code:
mysql_connect("your.hostaddress.com", "username", "password") or die(mysql_error()) ;
mysql_select_db("Database_Name") or die(mysql_error()) ;
Obviously you need to change the highlighted items to represent the actual values for your database.
Once you are connected to your database you can read data or write to your database.