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.
$GLOBALS
(PHP 4, PHP 5)
$GLOBALS — References all variables available in global scope
說明
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.
範例
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();
?>
上例的輸出類似於：
$foo in global scope: Example content $foo in current scope: local variable
註釋
Note:
"Superglobal" 也稱為自動的全域變數。這表示在腳本的所有範圍(scope)中都是可用的。不需要在函式或方法中用 global $variable; 來存取它。
Note: Variable availability
Unlike all of the other superglobals, $GLOBALS has essentially always been available in PHP.
add a note
User Contributed Notes 4 notes
therandshow at gmail dot com ¶
12 years ago
mstraczkowski at gmail dot com ¶
10 years ago
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";
vittorio.zamparella at famous googlemail ¶
7 years ago
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 ¶
8 years ago
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.
