全局變量不在PHP中的靜態類方法中更新

Question

我在PHP中遇到全局變量的問題。我的問題是，我在靜態類方法內改變的全局變量沒有在方法外部更新。

我已經包括了代碼：

test.php的

define('APP_ID', 'TESTING'); 
$_APP = array('test' => 'test value'); 
include ('appsettings.class.php'); 
AppSettings::initApplication(); 

appsettings.class.php

class AppSettings 
{ 
    public static function initApplication() 
    { 
    global $_APP; 
    session_start(); 

    // Some code here for your initializtions 
    self::initAppEngine(); 
echo '<pre>Inside initApplication: '; print_r($_APP); 
echo '<pre>Directly printing the session variable: '; print_r($_SESSION[APP_ID]); 
    } 

    private static function initAppEngine() 
    { 
    global $_APP; 

    if(isset($_SESSION[APP_ID])) 
    { 
     $_APP = &$_SESSION[APP_ID]; 
    } 
    else 
    { 
     $_SESSION[APP_ID] = array('abcd' => 'hello', 'APP_ID' => APP_ID); 
     $_APP = &$_SESSION[APP_ID]; 
die("Refresh the page"); 
    } 

    if (!isset($_APP['uid'])) 
     $_APP['uid'] = 0; 

echo '<pre>Inside initAppEngine: '; print_r($_APP); 
    } 
} 

$ _APP的舊值即將到來的新的代替在initApplication裏面。任何人都可以指出我做錯了什麼？

在此先感謝，

Answer 1

這很有趣。首先，請注意，它似乎什麼都沒有做與靜態方法：

$_SESSION['test'] = array("test value from superglobal"); 
$_APP = array('test' => "test value directly assigned"); 

class AppSettings 
{ 
    public static function initApplication() 
    { 
    global $_APP; 
    $_APP = &$_SESSION['test']; 
    echo '<pre>Inside initApplication: '; print_r($_APP); 
    } 

    public function initApplicationNonStatic() 
    { 
    global $_APP; 
    $_APP = &$_SESSION['test']; 
    echo '<pre>Inside initApplicationNonStatic: '; print_r($_APP); 
    } 
} 

echo '<pre>Before calling initApplication: '; print_r($_APP); 
AppSettings::initApplication(); 
echo '<pre>After calling initApplication: '; print_r($_APP); 
echo '<pre>Before calling initApplicationNonStatic: '; print_r($_APP); 
$appSettings = new AppSettings(); 
$appSettings->initApplicationNonStatic(); 
echo '<pre>After calling initApplicationNonStatic: '; print_r($_APP); 

結果：

Before calling initApplication: Array 
(
    [test] => test value directly assigned 
) 
Inside initApplication: Array 
(
    [0] => test value from superglobal 
) 
After calling initApplication: Array 
(
    [test] => test value directly assigned 
) 
Before calling initApplicationNonStatic: Array 
(
    [test] => test value directly assigned 
) 
Inside initApplicationNonStatic: Array 
(
    [0] => test value from superglobal 
) 
After calling initApplicationNonStatic: Array 
(
    [test] => test value directly assigned 
) 

但這個工程：

$_SESSION['test'] = array("test value from superglobal"); 
$_APP = array('test' => "test value directly assigned"); 

class AppSettings2 
{ 
    public function initApplicationNonStatic() 
    { 
    $GLOBALS['_APP'] = &$_SESSION['test']; // by reference 
    echo '<pre>Inside initApplicationNonStatic: '; print_r($GLOBALS['_APP']); 
    } 
} 

echo '<pre>Before calling initApplicationNonStatic: '; print_r($_APP); 
$appSettings2 = new AppSettings2(); 
$appSettings2->initApplicationNonStatic(); 
echo '<pre>After calling initApplicationNonStatic: '; print_r($_APP); 
$_SESSION['test'] = array("test value from superglobal altered"); 
echo '<pre>After altering superglobal: '; print_r($_APP); 

結果：

Before calling initApplicationNonStatic: Array 
(
    [test] => test value directly assigned 
) 
Inside initApplicationNonStatic: Array 
(
    [0] => test value from superglobal 
) 
After calling initApplicationNonStatic: Array 
(
    [0] => test value from superglobal 
) 
After altering superglobal: Array 
(
    [0] => test value from superglobal altered 
) 

這也適用：

$_SESSION['test'] = array("test value from superglobal"); 
$_APP = array('test' => "test value directly assigned"); 

class AppSettings2 
{ 
    public function initApplicationNonStatic() 
    { 
    global $_APP; 
    $_APP = $_SESSION['test']; // by value 
    echo '<pre>Inside initApplicationNonStatic: '; print_r($_APP); 
    } 
} 

echo '<pre>Before calling initApplicationNonStatic: '; print_r($_APP); 
$appSettings2 = new AppSettings2(); 
$appSettings2->initApplicationNonStatic(); 
echo '<pre>After calling initApplicationNonStatic: '; print_r($_APP); 
$_SESSION['test'] = array("test value from superglobal altered"); 
echo '<pre>After altering superglobal: '; print_r($_APP); 

結果：

Before calling initApplicationNonStatic: Array 
(
    [test] => test value directly assigned 
) 
Inside initApplicationNonStatic: Array 
(
    [0] => test value from superglobal 
) 
After calling initApplicationNonStatic: Array 
(
    [0] => test value from superglobal 
) 
After altering superglobal: Array 
(
    [0] => test value from superglobal // expected, since assigned by value 
) 

所以，似乎只要你想一個參考分配給一個函數或方法中的全局變量，你必須使用$GLOBALS['_APP']語法和你不能使用global $_APP。如果您不需要參考作業，則$GLOBALS['_APP']和global $_APP表現相同。

我不完全確定這是爲什麼; somepages是指這兩種結構的等價：

global $example; 
$example =& $GLOBALS['example']; 

這可能會導致在正確的軌道;不過，我希望你能用我的答案解決你的問題。