$_REQUEST not created when using variable variables?

php

Solution

(I tested with PHP 5.3.1)

One funny thing is that this portion of code :

<?php
var_dump(${'_' . 'REQUEST'});

Gets the notice `Undefined variable: _REQUEST`

But this one :

<?php
var_dump($_REQUEST);
var_dump(${'_' . 'REQUEST'});

Doesn't give any notice, and shows two empty arrays.

For a while, I though this could be related to `auto_globals_jit`, but `$_REQUEST` doesn't seem to the concerned by that directive... But there is one interested thing said, here :

Usage of SERVER and ENV variables is checked during the compile time so using them through e.g. variable variables will not cause their initialization.

Maybe, after all, even if it's not said in the manual, `auto_globals_jit` has an impact on `$_REQUEST`...

And, to be sure, I turned Off `auto_globals_jit` in my `php.ini` file :

; When enabled, the SERVER and ENV variables are created when they're first
; used (Just In Time) instead of when the script starts. If these variables
; are not used within a script, having this directive on will result in a
; performance gain. The PHP directives register_globals, register_long_arrays,
; and register_argc_argv must be disabled for this directive to have any affect.
; http://www.php.net/manual/en/ini.core.php#ini.auto-globals-jit
auto_globals_jit = Off

And tried this code again :

<?php

var_dump(${'_' . 'REQUEST'});

And I now get an empty array, and not a notice anymore.

So it seems `auto_globals_jit` does indeed have an impact on `$_REQUEST` -- even if it's not mentionned in the manual.

Problem

Consider the following snippets of code: Exhibit A: ``` $_REQUEST = json_decode(stripslashes(json_encode($_REQUEST, JSON_HEX_APOS)), true); ``` Exhibit B: ``` ${'_REQUEST'} = json_decode(stripslashes(json_encode(${'_REQUEST'}, JSON_HEX_APOS)), true); ``` Exhibit C: ``` ${'_' . 'REQUEST'} = json_decode(stripslashes(json_encode(${'_' . 'REQUEST'}, JSON_HEX_APOS)), true); ``` Both exhibit A and B work perfectly fine, exhibit C however displays a very strange error message: Notice: Undefined variable: _REQUEST What makes it even more weird is that this only happens with the `$_REQUEST` superglobal, if I try it with `$_GET`, `$_POST` or `$_COOKIE` all experiments work fine without raising error notices. I'm guessing this is a PHP bug? I'm running on `PHP 5.3.0`.

Original source