$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 20-Oct-2016 11:31


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 09:55


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 11-Jun-2013 05:58


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 06:32


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.