take dump of mysql database

<?php
$db_user = "****";
$db_pass = "*****";
$db_host = "localhost";
echo "<html>\n<p>Starting database(s) backup at : ". date("Y-m-d H:i:s");

        mysql_connect($db_host, $db_user, $db_pass);
        $r = mysql_query("show databases");
        while( $arr = mysql_fetch_array($r))
        {
            $db = $arr[0];
                    echo "\n\n<br>Exporting ".$db." at\n " . format_time() . "\n";
            echo shell_exec("mysqldump  -u ".$db_user." -h ".$db_host." -p".$db_pass." ".$db." | bzip2 > /home/mukesh/md/cron/06_db_backup/db_dump/".date('w')."_".$db.".sql.bz2");
        }

echo "\n\n<br>Database backup finished at : ". format_time() . "\n\n</html>"    ;
echo mysql_error();
mysql_close();
?>