3

我对 PHP 中的全局变量有疑问。我的问题是我在静态类方法内更改的全局变量没有在方法外更新。

我已经包含了代码：

测试.php

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 的旧值即将到来，而不是 initApplication 中的新值。谁能指出我做错了什么？

提前致谢，

4

1 回答 1

3

这很有趣。首先请注意，它似乎与静态方法无关：

$_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);

结果：

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
)

但这有效：

$_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);

结果：

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
)

这也有效：

$_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);

结果：

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
)

因此，似乎每当您想在函数或方法中分配对全局变量的引用时，都必须使用$GLOBALS['_APP']语法，而不能使用global $_APP. 如果您不需要通过引用进行分配，$GLOBALS['_APP']并且global $_APP行为相同。

我不确定为什么会这样；一些 页面提到了这两个结构的等价性：

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

这可能会导致正确的轨道；但是，我希望您可以通过我的回答解决您的问题。

于 2013-07-22T14:48:40.347 回答