If you need to connect to a mysql database from php you can do it like this:

<?php>
   $DBH = ‘localhost’;
   $DBU = ‘root’;
   $DBPWD = ‘password’;
   $DBN = ‘petstore’;
   $conn = mysql_connect($DBH, $DBU, $DBPWD) or die  ("Error: Could not connect to database.");
   mysql_select_db($dbname);
?>

This allows you to make a connection to the mysql database and gets it ready for you to make queries and manipulate the data.