Description:
------------
The PDO documentation page that lists the predefined constants,
/manual/en/pdo.constants.php, should note in the description of 
PDO::FETCH_KEY_PAIR that this feature was added in PHP 5.2.3.

See the NEWS in the source distribution for 5.2.8, for example.


Reproduce code:
---------------
function test()
{
    $dbh = new PDO("mysql:host=$GLOBALS[DEV_HOST];dbname=Fen", "fen", "xxxxxxx");
    $stmt = $dbh->prepare("select * from islands order by island_id");
    $stmt->execute();
    return $stmt->fetchAll(PDO::FETCH_KEY_PAIR);
}
var_dump(test());


Expected result:
----------------
I expected to get a returned array where the first column was the key of each array element.

Actual result:
--------------
In PHP 5.1.6, attempts to use PDO::FETCH_KEY_PAIR result in
PHP Fatal error:  Undefined class constant 'FETCH_KEY_PAIR'