MYSQL While with mysql_fetch_assoc not returning when =1

I have the following PHP that creates some JSON from a MySQL query. This works fine when there is more than one element i.e. mysql_fetch_assoc > 1 but if it = 1 then nothing works and debugging, any echo statements inside the while loop do not get called!

What is up with that?

$byFlight = mysql_query($query_byFlight, $pfArchiveDB) or die(mysql_error());
$row_byFlight = mysql_fetch_assoc($byFlight);
//$totalRows_byFlight = mysql_nu开发者_如何学编程m_rows($byFlight);
//echo ($query_byFlight);
$flights = array();
if(mysql_num_rows($byFlight)) {
    while($flight = mysql_fetch_assoc($byFlight)) {
        $flights[] = array('flight'=>$flight);
    }
}
header('Content-type: application/json');
echo json_encode(array('flights'=>$flights));

You are doing the fetch twice, and that consumes your first row perhaps. This code will work fine:

$byFlight = mysql_query($query_byFlight, $pfArchiveDB) or die(mysql_error());

 //$row_byFlight = mysql_fetch_assoc($byFlight); // <---- COMMENTED THIS FETCH

//$totalRows_byFlight = mysql_num_rows($byFlight);
//echo ($query_byFlight);
$flights = array();
if(mysql_num_rows($byFlight)) {
    while($flight = mysql_fetch_assoc($byFlight)) {
        $flights[] = array('flight'=>$flight);
    }
}
header('Content-type: application/json');
echo json_encode(array('flights'=>$flights));