$GLOBALS

$GLOBALS — 引用全局作用域中可用的全部变量

说明

一个包含了全部变量的全局组合数组。变量的名字就是数组的键。

范例

Example #1 $GLOBALS 范例

<?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();
?>

以上例程的输出类似于：

$foo in global scope: Example content
$foo in current scope: local variable

注释

Note:

"Superglobal"也称为自动化的全局变量。这就表示其在脚本的所有作用域中都是可用的。不需要在函数或方法中用 global $variable; 来访问它。

Note: 变量可用性

与所有其他超全局变量不同，$GLOBALS在PHP中总是可用的。

User Contributed Notes

vittorio.zamparella at famous googlemail 21-Oct-2016 08:31
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: http://www.php.net/manual/en/ini.core.php#ini.auto-globals-jit
-------------------------------------

http://www.php.net/manual/en/language.variables.variable.php
-------------------------------------
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.
-------------------------------------
stevenjeffries at gmail dot com 19-Nov-2015 06:55
I ran into the case where I needed to know if my script was in the global scope or not.

You can use $GLOBALS to figure out which case that is:

<?php // file foo.php

$some_unique_prefix_foo = "ok";
if (isset($GLOBALS["some_unique_prefix_foo"])) {
    echo "Foo is in global scope.\n";
} else {
    echo "Foo is NOT in global scope.\n";
}
unset($some_unique_prefix_foo);

// Inside another file.
function test() {
    include "foo.php";
}
test();

?>

Outputs:

Foo is in global scope.
Foo is NOT in global scope.
mstraczkowski at gmail dot com 12-Jun-2013 02:58
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";
therandshow at gmail dot com 29-Jun-2011 03:32
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.