PHP 7.0.26 Released

Using Register Globals

Warning

This feature has beenDEPRECATED as of PHP 5.3.0 and REMOVEDas of PHP 5.4.0.

Perhaps the most controversial change in PHP is when the default valuefor the PHP directive register_globals went from ON to OFF in PHP » 4.2.0. Reliance on thisdirective was quite common and many people didn't even know it existedand assumed it's just how PHP works. This page will explain how one canwrite insecure code with this directive but keep in mind that thedirective itself isn't insecure but rather it's the misuse of it.

When on, register_globals will inject your scripts with allsorts of variables, like request variables from HTML forms. Thiscoupled with the fact that PHP doesn't require variable initializationmeans writing insecure code is that much easier. It was a difficultdecision, but the PHP community decided to disable this directive by default. When on, people use variables yet really don't know for surewhere they come from and can only assume. Internal variables that aredefined in the script itself get mixed up with request data sent byusers and disabling register_globals changes this. Let's demonstratewith an example misuse of register_globals:

Example #1 Example misuse with register_globals=on

<?php
// define $authorized = true only if user is authenticated
if (authenticated_user()) {
    
$authorized true;
}

// Because we didn't first initialize $authorized as false, this might be
// defined through register_globals, like from GET auth.php?authorized=1
// So, anyone can be seen as authenticated!
if ($authorized) {
    include 
"/highly/sensitive/data.php";
}
?>

When register_globals=on, our logic above may be compromised. Whenoff, $authorized can't be set via request so it'llbe fine, although it really is generally a good programming practice toinitialize variables first. For example, in our example above we mighthave first done $authorized=false. Doing thisfirst means our above code would work with register_globals on or off asusers by default would be unauthorized.

Another example is that of sessions.When register_globals=on, we could also use$username in our example below but again you mustrealize that $username could also come from othermeans, such as GET (through the URL).

Example #2 Example use of sessions with register_globals on or off

<?php
// We wouldn't know where $username came from but do know $_SESSION is
// for session data
if (isset($_SESSION['username'])) {

    echo 
"Hello <b>{$_SESSION['username']}</b>";

} else {

    echo 
"Hello <b>Guest</b><br />";
    echo 
"Would you like to login?";

}
?>

It's even possible to take preventative measures to warn when forging isbeing attempted. If you know ahead of time exactly where a variableshould be coming from, you can check to see if the submitted data iscoming from an inappropriate kind of submission. While it doesn'tguarantee that data has not been forged, it does require an attacker toguess the right kind of forging. If you don't care where the requestdata comes from, you can use $_REQUEST as it containsa mix of GET, POST and COOKIE data. See also the manual section onusing variables from externalsources.

Example #3 Detecting simple variable poisoning

<?php
if (isset($_COOKIE['MAGIC_COOKIE'])) {

    
// MAGIC_COOKIE comes from a cookie.
    // Be sure to validate the cookie data!

} elseif (isset($_GET['MAGIC_COOKIE']) || isset($_POST['MAGIC_COOKIE'])) {

   
mail("admin@example.com""Possible breakin attempt"$_SERVER['REMOTE_ADDR']);
   echo 
"Security violation, admin has been alerted.";
   exit;

} else {

   
// MAGIC_COOKIE isn't set through this REQUEST

}
?>

Of course, simply turning off register_globals does not mean your codeis secure. For every piece of data that is submitted, it should also bechecked in other ways. Always validate your user data and initializeyour variables! To check for uninitialized variables you may turn uperror_reporting() to showE_NOTICE level errors.

For information about emulating register_globals being On or Off, see this FAQ.

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User Contributed Notes 12 notes

lester burlap
8 years ago
It would make this whole issue a lot less confusing for less-experienced PHP programmers if you just explained:

- $myVariable no longer works by default
- $_GET['myVariable'] works just fine

I'm embarrassed to say it's taken me six months since my ISP upgraded to PHP5 figure this out.  I've completely rewritten scripts to stop using GET variables altogether.

I'm dumb.
claude dot pache at gmail dot com
8 years ago
Beware that all the solutions given in the comments below for emulating register_global being off are bogus, because they can destroy predefined variables you should not unset. For example, suppose that you have

<?php $_GET['_COOKIE']=='foo'; ?>

Then the simplistic solutions of the previous comments let you lose all the cookies registered in the superglobal "$_COOKIE"! (Note that in this situation, even with register_global set to "on", PHP is smart enough to not mess predefined variables such as  $_COOKIE.)

A proper solution for emulating register_global being off is given in the FAQ, as stated in the documentation above.
tomas at hauso dot sk
1 year ago
for PHP5.4+ you can use registry pattern instead global

final class MyGlobal {
    private static $data=array();

    public static function get($key) {
        return (isset(static::$data[$key]) ? static::$data[$key] : null);
    }

    public static function set($key, $value) {
        static::$data[$key]=$value;
    }

    public static function has($key) {
        return isset(static::$data[$key]);
    }

}
// END OF CLASS

$var1='I wanna be global';

MyGlobal::set('bar', $var1 ); // set var to registry

function foo(){
    echo MyGlobal::get('bar'); // get var from registry
}

foo();
elitescripts2000 at yahoo dot com
4 years ago
<?php

/* Forces all GET and POST globals to register and be magically quoted.
* This forced register_globals and magic_quotes_gpc both act as if
* they were turned ON even if turned off in your php.ini file.
*
* Reason behind forcing register_globals and magic_quotes is for legacy
* PHP scripts that need to run with PHP 5.4 and higher.  PHP 5.4+ no longer
* support register_globals and magic_quotes, which breaks legacy PHP code.
*
* This is used as a workaround, while you upgrade your PHP code, yet still
* allows you to run in a PHP 5.4+ environment.
*
* Licenced under the GPLv2. Matt Kukowski Sept. 2013
*/

if (! isset($PXM_REG_GLOB)) {

 
$PXM_REG_GLOB =1;

  if (!
ini_get('register_globals')) {
    foreach (
array_merge($_GET, $_POST) as $key => $val) {
      global $
$key;
      $
$key =(get_magic_quotes_gpc()) ? $val : addslashes($val);
    }
  }
  if (!
get_magic_quotes_gpc()) {
    foreach (
$_POST as $key => $val) $_POST[$key]=addslashes($val);
    foreach (
$_GET as $key => $val$_GET[$key] =addslashes($val);
  }
}

?>
arman_y_92 at yahoo dot com
3 years ago
To all those fans of this insecure functionality (which I'm glad is now turned off by default) , you can just use extract() to achieve a similar goal more securely (unless you overwrite local variables with $_GET or $_POST data).
thewordsmith at hotmail dot com
2 years ago
//Some servers do not have register globals turned on. This loop converts $_BLAH into global variables.
foreach($_COOKIE as $key=> $value) {
    if(!is_array($value)){
        ${$key}=trim(rawurldecode($value));
        //echo "$key $value<br>";
    }
    else{
        ${$key}=$value;
    }
}
foreach($_GET as $key=> $value) {
    if(!is_array($value)){
        ${$key}=trim(rawurldecode($value));
        //echo "$key $value<br>";
    }
    else{
        ${$key}=$value;
    }
}
foreach($_POST as $key=> $value) {
    if(!is_array($value)){
        ${$key}=trim(rawurldecode($value));
        //echo "$key $value<br>";
    }
    else{
        ${$key}=$value;
    }
}
foreach($_REQUEST as $key=> $value) {
    if(!is_array($value)){
        ${$key}=trim(rawurldecode($value));
        //echo "$key $value<br>";
    }
    else{
        ${$key}=$value;
    }
}
foreach($_SERVER as $key=> $value) {
    if(!is_array($value)){
        ${$key}=trim(rawurldecode($value));
        //echo "$key $value<br>";
    }
    else{
        ${$key}=$value;
    }
}
chirag176 at yahoo dot com dot au
2 years ago
$mypost=secure($_POST);

function AddBatch($mypost,$Session_Prefix){
...
}
Ruquay K Calloway
9 years ago
While we all appreciate the many helpful posts to get rid of register_globals, maybe you're one of those who just loves it.  More likely, your boss says you just have to live with it because he thinks it's a great feature.

No problem, just call (below defined):

<?php register_globals(); ?>

anywhere, as often as you want.  Or update your scripts!

<?php
/**
* function to emulate the register_globals setting in PHP
* for all of those diehard fans of possibly harmful PHP settings :-)
* @author Ruquay K Calloway
* @param string $order order in which to register the globals, e.g. 'egpcs' for default
*/
function register_globals($order ='egpcs')
{
   
// define a subroutine
   
if(!function_exists('register_global_array'))
    {
        function
register_global_array(array $superglobal)
        {
            foreach(
$superglobal as $varname => $value)
            {
                global $
$varname;
                $
$varname =$value;
            }
        }
    }
   
   
$order =explode("\r\n", trim(chunk_split($order, 1)));
    foreach(
$order as $k)
    {
        switch(
strtolower($k))
        {
            case
'e':    register_global_array($_ENV);        break;
            case
'g':    register_global_array($_GET);        break;
            case
'p':    register_global_array($_POST);        break;
            case
'c':    register_global_array($_COOKIE);    break;
            case
's':    register_global_array($_SERVER);    break;
        }
    }
}
?>
moore at hs-furtwangen dot de
9 years ago
I had a look at the post from Dice, in which he suggested the function unregister_globals(). It didn't seem to work - only tested php 4.4.8 and 5.2.1 - so I made some tweaking to get it running. (I had to use $GLOBALS due to the fact that $$name won't work with superglobals).

<?php
//Undo register_globals
function unregister_globals() {
    if (
ini_get('register_globals')) {
       
$array =array('_REQUEST', '_FILES');
        foreach (
$array as $value) {
            if(isset(
$GLOBALS[$value])){
                foreach (
$GLOBALS[$value] as $key => $var) {
                    if (isset(
$GLOBALS[$key]) && $var ===$GLOBALS[$key]) {
                       
//echo 'found '.$key.'='.$var.' in $'.$value."\n";                   
                       
unset($GLOBALS[$key]);
                    }
                }
            }
        }
    }
}
?>

The echo was for debuging, thought it might come in handy.
steve at dbnsystems dot com
1 year ago
The following version could be even faster, unless anyone may come with a good reason why this wouldn't be a good practice:

<pre>
function unregister_globals() {
    if (ini_get(register_globals)) {
        $array=array('_REQUEST', '_SESSION', '_SERVER', '_ENV', '_FILES');
        foreach ($array as $value) {
            $$value=[];
        }
    }
}
</pre>
chirag
2 years ago
Fatal error: Cannot re-assign auto-global variable _POST

Final Solution for php 5.4 and above version

$a=  $_POST;
function add($_POST;){
echo $_POST['a'];
echo $_POST['b'];
}
add($a);
Dice
9 years ago
To expand on the nice bit of code Mike Willbanks wrote and Alexander tidied up, I turned the whole thing in a function that removes all the globals added by register_globals so it can be implemented in an included functions.php and doesn't litter the main pages too much.

<?php
//Undo register_globals
function unregister_globals() {
    if (
ini_get(register_globals)) {
       
$array =array('_REQUEST', '_SESSION', '_SERVER', '_ENV', '_FILES');
        foreach (
$array as $value) {
            foreach (
$GLOBALS[$value] as $key => $var) {
                if (
$var ===$GLOBALS[$key]) {
                    unset(
$GLOBALS[$key]);
                }
            }
        }
    }
}
?>
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