Moving to pdo_mysql as both pdo_sqlite and pdo_pgsql raise an exception, as expected. I haven't tested the other drivers, but I will attach a patch that adds a PDO Common test for the issue.

I experience this issue as well with dblib. Using SQL Server Profiler, I confirmed that it as indeed triggering exceptions at the DB level, but they are not being thrown by PDO. It seems inconsistent, in that I only get exceptions when executing a statement where I did something like forgetting to bind a parameter.

The following should demontrate the issue:

$conn = new PDO('dblib:host=XXX;dbname=XXX', 'REDACTED', 'REDACTED');
$conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

$stmt = $conn->prepare("SELECT thistable FROM doesnotexist");
try {
	$stmt->execute();
} catch (Exception $ex) {
	die("I am never reached");
}

The above WILL reach SQL Server, and emit an EventClass of "Exception", but PDO does not trickle it down to a PDOException. It's extremely unreliable.

The problem here seems to be specifically the case where a) emulated prepared statements are used and b) there are no placeholders in the query. In that case we hit an early bailout and don't validate the passed parameters.