如果使用存储过程需要PHP PDO PARAMS？

I'm new to PHP, but not programming. Have come from an ASP [classic] background. In brief, I'm using PHP 5.4, with FastCGI on IIS7 and SQL Server 2005 Express. I've learnt the fundamentals, and have spent quite some time looking into security.

I'm sanitising both GET and POST input data. My db connection strings are in a separate file placed outside the web root. I'm using PDO prepared statements [though I've heard query+quote perform faster] with named placeholders along with db stored procedures.

I'm trying to understand why I would need to use additional arguments within the bindParam function, particularly data type options "PDO::PARAM_STR, 12" [second argument in that example represent the data length right?].

What are the benefits of specifying the data type and length within the bindParam? Is it needed if I'm using stored procedures in which the data type and length is already specified? Also, I believe I need to use something like "PDO::PARAM_INPUT_OUTPUT" to return a value from a stored proc?

Thanks!

** EDIT **
For some reason, if I use the PDO::PARAM_STR argument, my stored procs don't seem to write data into the db. So I omitted that argument. Here's my code:

$sql1 = $conn->prepare("EXEC insert_platts :userAgent, :userIp, 1, :source");
$sql1->bindParam(':userAgent', $userAgent);
$sql1->bindParam(':userIp', $userIp);
$sql1->bindParam(':source', $source);
$sql1->execute();

Also, rather than returning the identity value from the stored proc, I'm using lastInsertId() instead:

$lastRow = $conn->lastInsertId();
print $lastRow;

No, data type and data length are not needed. I'm using mysql stored procs and the parameters are never typed values, all though I validate them of course. I guess that the reason is extra security and INOUT params. Quote:

To return an INOUT parameter from a stored procedure, use the bitwise OR operator to set the PDO::PARAM_INPUT_OUTPUT

have you tried this?

$params = array(
            ':userAgent'=>$userAgent,
            ':userIp' => $userIp,
            ':source' => $source
          );
$sql1 = $conn->prepare("EXEC insert_platts :userAgent, :userIp, 1, :source");
$sql1->execute($params);

About special characters: are you using correct encodings? I mean, the same encoding in the php app and the DB... sometimes is hard to work with one encoding in the scripts and other in the database.. and very often problems like that arise...