Description:
------------
The manual entry above is wrong.  The statement:
"Identical to mktime() except the passed parameters represents a GMT date."
should read
"Identical to mktime() except the timestamp produced represents a GMT date."

Here is a test case:
<?
// Assume month/day/year are set to today
$x = gmmktime(gmdate('H'),gmdate('i'),gmdate('s'),$month,$day,$year);
print ($x >= gmmktime()) ? "Yes" : "No";
?>
This produces "Yes" as the answer.  Changing it to:
<?
// Assume month/day/year are set to today
$x = gmmktime(date('H'),date('i'),date('s'),$month,$day,$year);
print ($x >= gmmktime()) ? "Yes" : "No";
?>
Produces the expected answer of "No"

Reproduce code:
---------------
<?
// Assume month/day/year are set to today
$x = gmmktime(gmdate('H'),gmdate('i'),gmdate('s'),$month,$day,$year);
print ($x >= gmmktime()) ? "Yes" : "No";
?>

Expected result:
----------------
No

Actual result:
--------------
Yes