PHPは、実行する全てのスクリプトに定義済みの多くの変数を 提供します。しかし、これらの変数の多くは、 実行するサーバーの種類、サーバーのバージョンおよび設定、 その他の要素に依存しており、完全に記述することはできません。 これらの変数のいくつかは、PHPを コマンドライン で実行した場合には利用できません。 これらの変数の一覧については、 定義済の変数 のセクションを参照ください。
PHP には、(使用する場合)Webサーバー、環境変数、 ユーザー入力からの変数を値とする定義済みの配列が追加されています。 これらの配列は、自動グローバル、すなわち、自動的に全ての スコープで利用可能であるという点でかなり特別です。このため、これらは "スーパーグローバル" といわれることもあります。 (PHPには、ユーザー定義のスーパーグローバルという機構はありません。) スーパーグローバルの一覧 も参照ください。
注意: 可変変数
可変変数として スーパーグローバルを使うことはできません。
variables_orderに ある変数が設定されていない場合、これらに対応するPHPの定義済み 変数も空のままとなります。
I haven't found it anywhere else in the manual, so I'll make a note of it here - PHP will automatically replace any dots ('.') in an incoming variable name with underscores ('_'). So if you have dots in your incoming variables, e.g.:
example.com/page.php?chuck.norris=nevercries
you can not reference them by the name used in the URI:
//INCORRECT
echo $_GET['chuck.norris'];
instead you must use:
//CORRECT
echo $_GET['chuck_norris'];I have this function in my main files, it allows for easier SEO for some pages without having to rely on .htaccess and mod_rewrite for some things.
<?php
function long_to_GET(){
/**
* This function converts info.php/a/1/b/2/c?d=4 TO
* Array ( [d] => 4 [a] => 1 [b] => 2 [c] => )
**/
if(isset($_SERVER['PATH_INFO']) && $_SERVER['PATH_INFO'] != ''){
//Split it out.
$tmp = explode('/',$_SERVER['PATH_INFO']);
//Remove first empty item
unset($tmp[0]);
//Loop through and apend it into the $_GET superglobal.
for($i=1;$i<=count($tmp);$i+=2){ $_GET[$tmp[$i]] = $tmp[$i+1];}
}
}
?>
Its probably not the most efficient, but it does the job rather nicely.
DD32- Security Issue and workaround -
If You use "eval()" to execute code stored in a database or elsewhere, you might find this tip useful.
Issue:
By default, all superglobals are known in every function.
Thus, if you eval database- or dynamically generated code (let's call it "potentially unsafe code"), it can use _all_ the values stored in _any_ superglobal.
Workaround:
Whenever you want to hide superglobals from use in evaluated code, wrap that eval() in an own function within which you unset() all the superglobals. The superglobals are not deleted by php in all scopes - just within that function. eg:
function safeEval($evalcode) {
unset($GLOBALS);
unset($_ENV);
// unset any other superglobal...
return eval($evalcode);
}
(This example assumes that the eval returns something with 'return')
In addition, by defining such a function outside classes, in the global scope, you'll make sure as well that the evaluated ('unsafe') code doesn't have access to the object variables ($this-> ...).It seems that when you wish to export a varible, you can do it as return $varible, return an array(), or globalise it. If you return something, information for that varible can only travel one way when the script is running, and that is out of the function.
function fn() {
$varible = "something";
return $variable;
}
echo fn();
OR
$newvariable = fn();
Although if global was used, it creates a pointer to a varible, whether it existed or not, and makes whatever is created in the function linked to that global pointer. So if the pointer was global $varible, and then you set a value to $varible, it would then be accessible in the global scope. But then what if you later on in the script redefine that global to equal something else. This means that whatever is put into the global array, the information that is set in the pointer, can be set at any point (overiden). Here is an example that might make this a little clearer:
function fn1() {
global $varible; // Pointer to the global array
$varible = "something";
}
fn1();
echo $varible; // Prints something
$varible = "12345";
echo $varible; // Prints 12345
function fn2() {
global $varible; // Pointer to the global array
echo $varible;
}
fn2(); // echos $varible which contains "12345"
Basically when accessing the global array, you can set it refer to something already defined or set it to something, (a pointer) such as varible you plan to create in the function, and later possibly over ride the pointer with something else.