How Do I Create A Mysql Connection Using Pdo?

<?php

// $host="localhost";
$username="root";
$password="";


$dbh=new PDO("mysql:host=localhost:8080; dbname=hemaslink",$username,$password);
if($dbh)
{
echo 'connected';
}
?>

Warning: PDO::__construct(): MySQL server has gone away in C:\wamp\www\Projects\connect.php on line 8

Fatal error: Uncaught exception 'PDOException' with message 'SQLSTATE[HY000] [2006] MySQL server has gone away' in C:\wamp\www\Projects\connect.php on line 8