stristr query trouble

[Ron Piggott <ron.php@xxxxxxxxxxxxxxxxxx>]

I am not understanding why 'true' isn't the result of this syntax because
$subjects equals:

$subjects = "Delivery Status Notification(Failure)";

Here is my syntax:

if ( stristr( $subjects, "Delivery Status Notifcation(Failure)" ) ) {
$TIRSFlag = true; 
echo "true";
}