jsonp crashing on php sql fetch

[Marius Miliunas]

I don't know why but I get the error:

"Uncaught SyntaxError: Unexpected token <"

where the while statement is. The statement works fine when i test the php on it's own in a browser but hits a road block here when used with ajax and jsonp

$query = "SELECT user_id FROM ng" . $uid . " WHERE user_id = '$req_id'";
$result = mysqli_query($dbc,$query);
while($row = mysqli_fetch_array($result)) { $row = "cheese"; }