Description:
------------
Perhaps it's intentional as variables aren't supposed to be numeric, but seeing as it's the $_SESSION array, I figured this would be allowed.  

Reproduce code:
---------------
<?php
session_start();

echo '<pre>';
print_r($_SESSION);
echo '<hr>';
$_SESSION[167]='hi world';
print_r($_SESSION);

echo '<a href="test1.php">Here ya go</a>';

?>

Expected result:
----------------
Array
(
    [167] => hi world
)Array
(
    [167] => hi world
)

Here ya go

Actual result:
--------------
Array
(
)
Array
(
    [167] => hi world
)

Here ya go