Query returns nothing through PHP

Question

I'm having trouble with my SQL query running through PHP. This is my code

$username = $_POST['username'];

$SQLString = "SELECT COUNT(*) FROM dbo.Users WHERE Username = '$username'";
$result = sqlsrv_query($conn, $SQLString) or die (print_r(sqlsrv_errors(), true));
$userExists = sqlsrv_fetch_object( $result );

echo("test");
echo($userExists);
echo("test2");

This returns testtest2, and nothing for $userExists. This seemed to work last night, and I haven't changed anything besides printing out the sqlsrv errors, but those don't return anything.

$result returns Resource id #3, and I'm able to run an insert later in my code.

Can anyone see why $userExists returns nothing at all? I thought that it would have to return 0 at the very least (if the user does not exist).

EDIT

So attempting using prepared statements that chris85 recommended, and again it spits out the exact same thing. $stmt returns Resource ID #2, and $userExists returns absolutely nothing. No failures, no errors.

$SQLString = "SELECT COUNT(*) FROM dbo.Users WHERE Username = '$username'";
$stmt = sqlsrv_prepare( $conn, $SQLString, array( &$qty, &$id));
$userExists = sqlsrv_fetch_object( $stmt);
if( !$stmt ) {
    die( print_r( sqlsrv_errors(), true));
}

echo("test");
print_r($stmt);
print_r($userExists);   
echo("test2");