Global variable not updating inside static Class method in PHP

Questions

I have a problem with global variables in PHP. My problem is that a global variable that I change inside a static class method isn t updating outside the method.

I ve included the code:

test.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);
  }
}

The old value of $_APP is coming instead of the new one inside initApplication. Can anyone point out what I m doing wrong?

Thanks in advance,

Answers

This is quite interesting. First of all, note that it seems to have nothing to do with static methods:

$_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);

Result:

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
)

But this works:

$_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);

Result:

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
)

And this works, too:

$_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);

Result:

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
)

So, it seems that whenever you want to assign a reference to a global variable inside a function or method, you have to use the $GLOBALS[ _APP ] syntax and you cannot use global $_APP. If you don t need the assignment by reference, $GLOBALS[ _APP ] and global $_APP behave the same.

http://code.stephenmorley.org/php/references-tutorial/ http://code.stephenmorley.org/php/references-tutorial/

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

This might lead to the right track; however, I hope that you can troubleshoot your problem with my answer.

Source

License : cc by-sa 3.0

http://stackoverflow.com/questions/17784930/global-variable-not-updating-inside-static-class-method-in-php

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