International PHP Conference 2019 - Spring Edition


SuperglobalsSuperglobals son variables internas que están disponibles siempre en todos los ámbitos


Algunas variables predefinidas en PHP son "superglobales", lo que significa que están disponibles en todos los ámbitos a lo largo del script. No es necesario emplear global $variable; para acceder a ellas dentro de las funciones o métodos.

Las variables superglobals son:

Historial de cambios

Versión Descripción
4.1.0 Las superglobals son añadidas a PHP.


Nota: Disponibilidad de variables

Por defecto, todas las superglobals están disponibles pero hay directivas que afectan a su disponibilidad. Para más información, véase la documentacion de variables_order.

Nota: Tratando con register_globals

Si la directiva obsoleta register_globals tiene el valor on entonces las variables están tambien disponibles en el ámbito global del código. Por ejemplo, $_POST['foo'] tambien existirá como $foo.

Para información relacionada, consulte el FAQ titulado "¿Cómo puede afectarme register_globals?"

Nota: Variables variables

Las variables superglobals no pueden ser usadas como variables variables dentro de funciones o métodos de clase.

add a note add a note

User Contributed Notes 5 notes

5 years ago
Since PHP 5.4, you cannot use a superglobal as the parameter to a function. This causes a fatal error:

function foo($_GET) {
  // whatever

It's called "shadowing" a superglobal, and I don't know why people ever did it, but I've seen it out there. The easy fix is just to rename the variable $get in the function, assuming that name is unique.

There was no deprecation warning issued in previous versions of PHP, according to my testing, neither in 5.3 nor 5.2. The error messages in 5.4 are:
Fatal error: Cannot re-assign auto-global variable _GET in...
Fatal error: Cannot re-assign auto-global variable _COOKIE in...
php (a)
1 year ago
For those wondering if register_globals also makes global variables available inside functions - it doesn't.

Running this code on a PHP52 webserver with register_globals enabled, using url:

function abc() {
"in func: '$hello' \n"; // outputs "in func: '' "
"global: '$hello' \n"; // outputs "global: 'campers' "
John Slegers
4 years ago
Want to know how to generate a formatted list with all globals (including custom ones)? Check out the code below.

// Generate a formatted list with all globals
// Custom global variable $_CUSTOM
$_CUSTOM = array('USERNAME' => 'john', 'USERID' => '18068416846');

// List here whichever globals you want to print
// This could be your own custom globals
$globals = array(
'$_SERVER' => $_SERVER, '$_ENV' => $_ENV,
'$_REQUEST' => $_REQUEST, '$_GET' => $_GET,
'$_POST' => $_POST, '$_COOKIE' => $_COOKIE,
'$_FILES' => $_FILES, '$_CUSTOM' => $_CUSTOM
        <?php // Adjust CSS formatting for your output  ?>
        .left {
            font-weight: 700;
        .right {
            font-weight: 700;
            color: #009;
        .key {
            color: #d00;
            font-style: italic;
// Generate the output
echo '<h1>Superglobals</h1>';
        foreach (
$globals as $globalkey => $global) {
'<h3>' . $globalkey . '</h3>';
            foreach (
$global as $key => $value) {
'<span class="left">' . $globalkey . '[<span class="key">\'' . $key . '\'</span>]</span> = <span class="right">' . $value . '</span><br />';
lskatz at gmail dot com
10 years ago
It's not a good idea to use $_ENV unless you are specifying an environmental variable.  This is probably a better example that I found on another page in

function test() {
$foo = "local variable";

'$foo in global scope: ' . $GLOBALS["foo"] . "\n";
'$foo in current scope: ' . $foo . "\n";

$foo = "Example content";
serpent at paradise dot net dot nz
6 years ago
You can go the other way as well i.e.

function test() {
$GLOBALS['foo'] = "Example content";


This doesn't appear to be affected by register_globals, I have it switched off.
To Top