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PHP 4.1.0 Release Announcement

After a lengthy QA process, PHP 4.1.0 is finally out!
[ Version Française ]

PHP 4.1.0 includes several other key improvements:

As some of you may notice, this version is quite historic, as it's the first time in history we actually incremented the middle digit! :) The two key reasons for this unprecedented change were the new input interface, and the broken binary compatibility of modules due to the versioning support.

Following is a description of the new input mechanism. For a full list of changes in PHP 4.1.0, see the ChangeLog.


SECURITY: NEW INPUT MECHANISM

First and foremost, it's important to stress that regardless of anything you may read in the following lines, PHP 4.1.0 still supports the old input mechanisms from older versions. Old applications should go on working fine without modification!

Now that we have that behind us, let's move on :)

For various reasons, PHP setups which rely on register_globals being on (i.e., on form, server and environment variables becoming a part of the global namespace, automatically) are very often exploitable to various degrees. For example, the piece of code:

<?php
if (authenticate_user()) {
 
$authenticated = true;
}
...
?>

May be exploitable, as remote users can simply pass on 'authenticated' as a form variable, and then even if authenticate_user() returns false, $authenticated will actually be set to true. While this looks like a simple example, in reality, quite a few PHP applications ended up being exploitable by things related to this misfeature.

While it is quite possible to write secure code in PHP, we felt that the fact that PHP makes it too easy to write insecure code was bad, and we've decided to attempt a far-reaching change, and deprecate register_globals. Obviously, because the vast majority of the PHP code in the world relies on the existence of this feature, we have no plans to actually remove it from PHP anytime in the foreseeable future, but we've decided to encourage people to shut it off whenever possible.

To help users build PHP applications with register_globals being off, we've added several new special variables that can be used instead of the old global variables. There are 7 new special arrays:

Now, other than the fact that these variables contain this special information, they're also special in another way - they're automatically global in any scope. This means that you can access them anywhere, without having to 'global' them first. For example:

<?php
function example1()
{
    print
$_GET["name"];   // works, 'global $_GET;' is not necessary!
}
?>

would work fine! We hope that this fact would ease the pain in migrating old code to new code a bit, and we're confident it's going to make writing new code easier. Another neat trick is that creating new entries in the $_SESSION array will automatically register them as session variables, as if you called session_register(). This trick is limited to the session module only - for example, setting new entries in $_ENV will not perform an implicit putenv().

PHP 4.1.0 still defaults to have register_globals set to on. It's a transitional version, and we encourage application authors, especially public ones which are used by a wide audience, to change their applications to work in an environment where register_globals is set to off. Of course, they should take advantage of the new features supplied in PHP 4.1.0 that make this transition much easier.

As of the next semi-major version of PHP, new installations of PHP will default to having register_globals set to off. No worries! Existing installations, which already have a php.ini file that has register_globals set to on, will not be affected. Only when you install PHP on a brand new machine (typically, if you're a brand new user), will this affect you, and then too - you can turn it on if you choose to.

Note: Some of these arrays had old names, e.g. $HTTP_GET_VARS. These names still work, but we encourage users to switch to the new shorter, and auto-global versions.

Thanks go to Shaun Clowes (shaun at securereality dot com dot au) for pointing out this problem and for analyzing it.

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