PDO cannot find ODBC driver - oracle

Question

Trying to migrate to PDO for an ODBC connection to a remote database.
My system is Windows 7 Pro, with a FortiClient VPN connection to the remote domain, and Tunnel Mode connected. (Added in edit: Running PHP 5.4, so PDO should be installed by default.)
The data source configuration in the Windows 7 ODBC Data Source Administrator is as follows (some names changed for security):
Under System DSN:
System Data Source Name = 'TheBigDB'
Driver = 'Oracle in instantclient_11_2' (64-bit)
TNS Service Name = '10.10.1.20:1521/BIGDB'
UserID = 'BigDBUser'
All other settings are defaults for installation of driver
The following piece of PHP non-PDO code is able to create a connection usable for queries:
if (!($myConn = odbc_connect('TheBigDB','BigDBUser','myPwd'))) {
echo "No ODBC connection<br />";
}
So I can connect to the database. The problem is doing it in PDO. The following PHP...
try {
$odbcConn = new PDO('odbc:Driver={Oracle in instantclient_11_2};Server=10.10.1.20:1521;Database=BIGDB;Uid=BigDBUser;Pwd=myPwd');
} catch (PDOException $e) {
echo 'PDO connection failed: ' . $e->getMessage();
}
... results in a PDO connection failed: could not find driver message. My first try relied more heavily on the Data Sources Administrator; that looked like this:
try {
$odbcConn = new PDO('MyBigDB','BigDBUser','myPwd');
} catch (PDOException $e) {
echo 'PDO connection failed: ' . $e->getMessage();
}
Same thing -- could not find driver.
So here's my question: Given a Windows 7 system with ODBC through a VPN connection to an Oracle database that all seems to work without PDO, how do I migrate the connection parameters to create a PDO connection? Maybe a better question is why mess with PDO for the connection, but I keep reading that PDO is more secure, so I'm trying to use it.

Answer 1

More digging got me an answer. The correct syntax for creating a PDO object that uses a Windows Data Sources ODCB connection is not what I showed, but instead this (minus the try/catch):
$myConn = new PDO('odbc:TheBigDB','BigDBUser','myPwd');
BUT... with PHP 5.4.12 using ODBC to touch an Oracle 11 DB, you need to edit the correct php.ini file (see this WampServer forum topic for a discussion of which of three php.ini files you need to edit). Under Dynamic Extensions, uncomment extension=php_pdo_odbc.dll and extension=php_pdo_oci.dll (I did both; not sure which one did the trick...)
Another tip: In my scripts, neither odbc_connect() nor PDO() worked for me unless my connection was created in Windows Data Sources Administrator under the System DSN tab. It did not work under User DSN.