A simple php script to open a connection to a database

$dbhost = 'localhost';
$dbuser = 'db username';
$dbpass = 'db password';

$conn = mysql_connect($dbhost, $dbuser, $dbpass) or die ('Error connecting to mysql');

$dbname = 'db name';
mysql_select_db($dbname);
?>

Save this as .php and then whenever you want to access the database, just add

include '.php'

to the top of a php script and the database can be queried using standard sql commands.