php - pdo_oci driver not found but is listed in available drivers

I am trying to connect to an Oracle Database 11g XE running on windows from a remote Ubuntu 14.04 server using PDO_OCI in php. I followed this guide http://gist.github.com/tassoevan/10392954 (numerous times) and keep getting the following error:

could not find driver

However when I call PDO::getAvailableDrivers() it gives me this:

Array ( [0] => mysql [1] => oci [2] => sqlite )

Note: oci wasn't there before I followed the guide in the link above.

All of the other tutorials I could find were basically the same thing.

I have the Oracle instant client installed (version 11.1). The latest version was not even getting the driver to show up in the list of available drivers.

Also I know that the driver which is used in this method is older but there are no step by step guides on how to get it working with the lastest one. I am new to Oracle Databases as well as php so step by step help would be greatly appreciated.

UPDATE: I figured out the driver problem. It was in my php code, and something very silly. I am posting for the benefit of others.

My original code had "OCI" in capital letters when setting the connection.

$tns = "  
(DESCRIPTION =
    (ADDRESS_LIST =
      (ADDRESS = (PROTOCOL = TCP)(HOST = myIP)(PORT = 1521))
    )
    (CONNECT_DATA =
      (SERVICE_NAME = XE)
    )
  )
       ";

try{
$pdo = new PDO('OCI:dbname='.$tns ,'username','password'); // Capital 'OCI' here is WRONG so changed to 'oci:dbname='
} catch(PDOException $e){
    echo $e->getMessage();
}

print_r(PDO::getAvailableDrivers());
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However, I am having problems querying the Database. It seems nothing is happening. I have allowed the port 1521 in the Windows firewall for both incoming and outgoing. Any suggestion?

Here is my php code:

$stmt = $pdo->prepare("SELECT * FROM `PDO`;");
$stmt->execute();
$result = $stmt->fetchColumn(0);
echo $result;
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The tablePDO only has one column with one row.

Does the Oracle database need to be configured to allow for remote connections?