Try using:
$oStatement->bindParam(':TestID', $iTestID);
instead of:
$oStatement->bindParam(':TestID', $iTestID,PDO::PARAM_INT );
The latter is implicitly binding for output, which might be part of your problem.

Hey Wez, I never saw the feedback til I stumbled on it today, and clearly have been able to work around this, but it does keep stopping me.

It happens exactly the same if I omit the PDO::PARAM_INT as the final parameter.

I am still using the branched version you gave me... I'd be happy to test with the latest if you think it might be fixed there.

--Travis

This bug affects my app, too. I'm using PHP 5.2.3 on Windows XP Pro SP2, under both IIS 5.1 and Apache 2.2, with SQL Server 2005 Express.

I don't know if it'll help or not, but here's some more reproduce code. Just fix the PDO DSN string to something valid.

<?php
$db = new PDO("odbc:dsn=$odbcDsn;uid=$user;pwd=$pass");

$createTable = 
    'CREATE TABLE ##test (
        intCol int,
        textCol varchar(20)
    )';
$createTable2 =
    'CREATE TABLE ##test2 (
        intCol2 int,
        textCol2 varchar(20)
    )';
$db->exec($createTable);
$db->exec($createTable2);

$ins = $db->prepare('INSERT INTO ##test (intCol, textCol) VALUES (:i, :t)');
$ins->execute(array('i'=>1, 't'=>'A String'));
$ins2 = $db->prepare('INSERT INTO ##test2 (intCol2, textCol2) VALUES (:i, :t)');
$ins2->execute(array('i'=>1, 't'=>'Another String'));

$sel = $db->prepare('SELECT * FROM ##test WHERE intCol = (SELECT intCol2 FROM ##test2 WHERE textCol2 = :t)');
$sel->execute(array('t'=>'Another String')) or var_dump($sel->errorInfo());

$sel = $db->prepare('SELECT * FROM ##test WHERE intCol = (SELECT intCol2 FROM ##test2 WHERE intCol2 = :i)');
$sel->execute(array('i'=>1)) or var_dump($sel->errorInfo());

$sel = $db->prepare('SELECT * FROM ##test WHERE intCol = (SELECT intCol2 FROM ##test2 WHERE textCol2 = :t)');
$sel->bindValue('t', 'Another String');
$sel->execute() or var_dump($sel->errorInfo());

$sel = $db->prepare('SELECT * FROM ##test WHERE intCol = (SELECT intCol2 FROM ##test2 WHERE intCol2 = :i)');
$sel->bindValue('i', 1);
$sel->execute() or var_dump($sel->errorInfo());

$sel = $db->prepare('SELECT * FROM ##test WHERE intCol = (SELECT intCol2 FROM ##test2 WHERE textCol2 = :t)');
$sel->bindValue('t', 'Another String', PDO::PARAM_STR);
$sel->execute() or var_dump($sel->errorInfo());

$sel = $db->prepare('SELECT * FROM ##test WHERE intCol = (SELECT intCol2 FROM ##test2 WHERE intCol2 = :i)');
$sel->bindValue('i', 1, PDO::PARAM_INT);
$sel->execute() or var_dump($sel->errorInfo());

$sel = $db->prepare('SELECT * FROM ##test WHERE intCol = (SELECT intCol2 FROM ##test2 WHERE textCol2 = :t)');
$t = 'Another String';
$sel->bindParam('t', $t, PDO::PARAM_STR);
$sel->execute() or var_dump($sel->errorInfo());

$sel = $db->prepare('SELECT * FROM ##test WHERE intCol = (SELECT intCol2 FROM ##test2 WHERE intCol2 = :i)');
$i = 1;
$sel->bindParam('i', $i, PDO::PARAM_INT);
$sel->execute() or var_dump($sel->errorInfo());
?>

the problem still occurs on:
PHP 5.2.4 (cli) (built: Aug 30 2007 07:06:31)

Very nice that you didn't bother trying with the RCs..

Assigned to the maintainer.

I was able to reproduce this error using the 2008-01-05 snapshot of PDO_ODBC.

Reproduce code:
---------------
<?php
$db = new PDO('odbc:Driver={SQL Server}; Server=localhost; Uid=test; Pwd=test; Database=test;');
$db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$db->exec('CREATE TABLE #foo (id INT NOT NULL)');
$db->exec('INSERT INTO #foo VALUES(1)');
$stmt = $db->prepare('SELECT id FROM #foo WHERE id IN (SELECT id FROM #foo WHERE id = ?)');
$stmt->bindValue(1, 1, PDO::PARAM_INT);
$stmt->execute();
var_dump($stmt->fetch(PDO::FETCH_ASSOC));
?>

Expected result:
----------------
array(1) { ["id"]=>  string(1) "1" }

Actual result:
--------------
PHP Fatal error: Uncaught exception 'PDOException' with message 'SQLSTATE[42000]: Syntax error or access violation: 306 [Microsoft][ODBC SQL Server Driver][SQL Server]The text, ntext, and image data types cannot be compared or sorted, except when using IS NULL or LIKE operator. (SQLExecute[306] at ..\pecl_5_2\pdo_odbc\odbc_stmt.c:133)'

A trace using the Profiler tool shows that the bound integer value is incorrectly interpreted as text:

CREATE TABLE #foo (id INT NOT NULL)
go
INSERT INTO #foo VALUES(1)
go
declare @P1 int
set @P1=NULL
exec sp_prepare @P1 output, N'@P1 text', N'SELECT id FROM #foo WHERE id IN (SELECT id FROM #foo WHERE id = @P1)', 1
select @P1
go

Incorrect: N'@P1 text'
It should be: N'@P1 int'

This appears to be a bug with prepared statements in the underlying microsoft client driver implementation...

Even the microsoft SQL Server 2005 Driver for php suffers from this bug

<?php
$iTestID=1;
$connection = sqlsrv_connect($dsn);
$statement = sqlsrv_prepare($connection,
	'SELECT TestID FROM zTest_TBL WHERE TestID IN (SELECT TestID FROM zTest_TBL WHERE TestID = ?)',
	array($iTestID));
$value = sqlsrv_execute($statement);
print_r(sqlsrv_errors());
?>

so it appears the issue is upstream and we have to wait for microsoft..

Not PHP bug -> bogus.

This is caused by a long standing MS SQL ODBC Client bug.  http://connect.microsoft.com/SQLServer/feedback/details/521409/odbc-client-mssql-does-not-work-with-bound-parameters-in-subquery

Last update on 8/3/2010 was that it would be resolved in a future release of the SQL Server Native Access Client.