unable to create database, showing unknown database

The application is only able to connect with a manually developed database in phpmyadmin but not able to create a database from the php.

here is the code (install_database.php) for creating that database

<?php
$cn = mysql_connect('localhost','root','') or
        die('Unable to connect. Check connection parameters.');

$sql = 'CREATE DATABASE IF NOT EXISTS cars';

mysql_query($sql, $cn) or 
        die(mysql_error($cn));

mysql_select_db('cars') or
        die(mysql_error($cn));

$sql = 'CREATE TABLE IF NOT EXISTS user (
            user_id             INTEGER UNSIGNED        NOT NULL AUTO_INCREMENT,
            user_username       VARCHAR(80)             NOT NULL,
            user_password       VARCHAR(80)             NOT NULL,
            user_join_date      INTEGER UNSIGNED        NOT NULL,
            user_age            INTEGER UNSIGNED        NOT NULL,
            user_country        VARCHAR(100)            NOT NULL,

            PRIMARY KEY (user_id)
            )
            ENGINE=MyISAM';

mysql_query($sql,$cn) or 
        die(mysql_error($cn));



?>

its showing unknown database 'cars' on the browser. if any additional detail is required please inform.