Description:
------------
PHP normally replaces spaces, periods, and unclosed [ with underscores in $_GET/$_POST/$_REQUEST. After an unclosed [, it ceases to do this.

Reproduce code:
---------------
/*
With a url like ?x[ x=x
*/
print_r($_GET);

Expected result:
----------------
Array
(
    [x__x] => x
)


Actual result:
--------------
Array
(
    [x_ x] => x
)