MySql database connection by PHP Data Objects (PDO)

Connections are established by creating instances of the PDO base class. It doesn't matter which driver you want to use; you always use the PDO class name. The constructor accepts parameters for specifying the database source (known as the DSN) and optionally for the username and password (if any).

Syntax:
  $varname=new PDO($dsn, $username, $passwd, $options)

Example:
<?php
$dbh = new PDO('mysql:host=localhost;dbname=test',$user,$pass);
?>

Example  for closing connection

<?php
$dbh = new PDO('mysql:host=localhost;dbname=test', $user, $pass);// use the connection here


// and now we're done; close it$dbh = null;?>