access data in php

If I gather the sql results with this code
$results = pg_query($dbconn,$query);

I can check if there is no returned data with this code
$rows = pg_fetch_assoc($result);

but if I then use a while loop to display data (if there is data returned) with this code
while ($row = pg_fetch_array($result)){ . . . }

I have to execute this code a second time before the while loop
$results = pg_query($dbconn,$query);

If I do not execute the $results line a second time the while loop does not work properly.

Why is $results loosing its value when it hits the while loop?

Thanks

Marc