How to connect mysql database in PHP?

<?php
$server="localhost";
$dbname="mydb";
$username="root";
$password="";

$connection=mysql_connect($server,$username,$password);

if(!$connection)
{
die("couldnot connected:".mysql_error());
}
if(mysql_query("create database mydb",$connection))
{
echo "database created";
}
else
{
echo die("database create faild".mysql_error());
}
?>