How to send bytea data straight to browser (as in pg_loreadall)?

I don't seem to be able to get my head 'round as to how to do this. It
works OK if I do something like

---------------------- begin snippet ----------------------
$query = "SELECT * FROM bytea_test;";

$conn = pg_pconnect("host=192.168.100.70 dbname=bytea_test");
$result = pg_exec($conn, $query);

$i = 0;
while (@pg_result($result, $i, id)) {

    $fp = fopen('/usr/local/httpd/htdocs/testfile'.$i.'.gif', 'w');
    fwrite($fp, stripcslashes(pg_result($result, $i, image)));
    echo "<img src=\"";
    echo 'testfile'.$i.'.gif';
    echo "\">";
    $i++;

}
---------------------- end snippet ----------------------

which means that I create a file for each image pulled from the database
and then put this file path (relative to http root) into an img tag.

That's rather stupid though, because it's unnecessary, slow, and bound
to give concurrency trouble.

I've played with fgets, fwrite, fputs, fpassthrough, trying to make a
file pointer on stdout with fopen . . . it appears that I don't
understand some crucial point about how this works. How do you present
an image to the browser without actually creating a file for it? The
built in function pg_loreadall appears to do exactly that. I'd need to
replicate that functionality for bytea.

Regards, Frank