PHP - Php And Oracle 10g Configration Help

hello every body,

I am trying to connect the oracle 10g with PHP code but my all code get error and does not get connection from the server database so i need the help from your site.
can you help me

My Code is:-

<?php

$db_host="xxx.xxx.xx.xxx"; // Host name
$db_username="xxx"; // Mysql username
$db_password="xxx"; // Mysql password
$db_name="XE"; // Database name
$tbl_name="USER_DETAIL"; // Table name

// Connect to server and select database.
try
{
   $conn = "(DESCRIPTION=(ADDRESS_LIST = (ADDRESS = (PROTOCOL = TCP)(HOST = xxx.xxx.xx.xxx)(PORT = 1521)))(CONNECT_DATA=(SERVER=DEDICATED)(SERVER_NAME=MYDB)))" ;
   $c= oci_connect($db_username, $db_password, $conn);
   $d=new PDO("oci:db_name=$conn",$db_username, $db_password);   
}
catch(PDOException $e)
{   
      trigger_error("Could not connect to database",E_USER-ERROR);   
}