$GLOBALS
(PHP 4, PHP 5)
$GLOBALS — References all variables available in global scope
Description
An associative array containing references to all variables which are currently defined in the global scope of the script. The variable names are the keys of the array.
Examples
Example #1 $GLOBALS example
<?php
function test() {
$foo = "local variable";
echo '$foo in global scope: ' . $GLOBALS["foo"] . "\n";
echo '$foo in current scope: ' . $foo . "\n";
}
$foo = "Example content";
test();
?>
The above example will output something similar to:
$foo in global scope: Example content $foo in current scope: local variable
Notes
Note:
This is a 'superglobal', or automatic global, variable. This simply means that it is available in all scopes throughout a script. There is no need to do global $variable; to access it within functions or methods.
Note: Variable availability
Unlike all of the other superglobals, $GLOBALS has essentially always been available in PHP.
- Функция Суперглобальные переменные() - Суперглобальные переменные - это встроенные переменные, которые всегда доступны во всех областях видимости
- Функция $GLOBALS() - Ссылки на все переменные глобальной области видимости
- Функция $_SERVER() - Информация о сервере и среде исполнения
- Функция $_GET() - GET-переменные HTTP
- Функция $_POST() - HTTP POST variables
- Функция $_FILES() - Переменные файлов, загруженных по HTTP
- Функция $_REQUEST() - Переменные HTTP-запроса
- Функция $_SESSION() - Переменные сессии
- Функция $_ENV() - Переменные окружения
- Функция $_COOKIE() - HTTP Куки
- Функция $php_errormsg() - Предыдущее сообщение об ошибке
- Функция $HTTP_RAW_POST_DATA() - Необработанные POST-данные
- Функция $http_response_header() - Заголовки ответов HTTP
- Функция $argc() - Количество аргументов переданных скрипту
- Функция $argv() - Массив переданных скрипту аргументов
Коментарии
As of PHP 5.4 $GLOBALS is now initialized just-in-time. This means there now is an advantage to not use the $GLOBALS variable as you can avoid the overhead of initializing it. How much of an advantage that is I'm not sure, but I've never liked $GLOBALS much anyways.Watch out when you are trying to set $GLOBALS to the local variable.
Even without reference operator "&" your variable seems to be referenced to the $GLOBALS
You can test this behaviour using below code
<?php
/**
* Result:
* POST: B, Variable: C
* GLOBALS: C, Variable: C
*/
// Testing $_POST
$_POST['A'] = 'B';
$nonReferencedPostVar = $_POST;
$nonReferencedPostVar['A'] = 'C';
echo 'POST: '.$_POST['A'].', Variable: '.$nonReferencedPostVar['A']."\n\n";
// Testing Globals
$GLOBALS['A'] = 'B';
$nonReferencedGlobalsVar = $GLOBALS;
$nonReferencedGlobalsVar['A'] = 'C';
echo 'GLOBALS: '.$GLOBALS['A'].', Variable: '.$nonReferencedGlobalsVar['A']."\n\n";
I finally found information about superglobals not being found in $GLOBALS:
https://bugs.php.net/bug.php?id=65223&edit=2
-------------------------------------
[2013-07-09 12:00 UTC] johannes @php.net
[...]super-globals (aka. auto globals) are not added to symbol tables by default for performance reasons unless the parser sees need. i.e.
<?php
$_SERVER;
print_r($GLOBALS);
?>
will list it. You can also control this using auto_gloals_jit in php.ini: ini.core#ini.auto-globals-jit
-------------------------------------
language.variables.variable
-------------------------------------
Warning
Please note that variable variables cannot be used with PHP's Superglobal arrays within functions or class methods. The variable $this is also a special variable that cannot be referenced dynamically.
-------------------------------------
We can be more clear with the extension of the given example.
Before PHP Version 8.1
<?php
$a = 1;
$globals = $GLOBALS;
$globals['a'] = 2;
echo $a; // 2
echo $globals['a']; // 2
echo $GLOBALS['a']; // 2
?>
After PHP Version 8.1
<?php
$a = 1;
$globals = $GLOBALS;
$globals['a'] = 2;
echo $a; // 1
echo $globals['a']; // 2
echo $GLOBALS['a']; // 1
?>