Description:
------------
A session variable can be created containing a '!', but the entire session is destroyed when the system tries to write the session file.

Test script:
---------------
<?php
session_start();
$_SESSION['as!df'] = array("test 123");
// print_r on _SESSION here shows expected result.
session_write_close();
session_start();
echo "<pre>".print_r($_SESSION,true)."</pre>";


Expected result:
----------------
Array
(
    [as!df] => Array
        (
            [0] => test 123
        )

)


Actual result:
--------------
Array
(
)