How to share a dynamic variable between files in PHP(5)? - php

Question

I have an object of some class that obeys the singleton pattern. I need to initialize it in one file and then use it in others. I don't know how to do this, here is what I tried :
//myClass.php
class myClass
{
private static $instance = null;
private function __construct($args)
{
//stuff
}
public function Create($args)
{
self::$instance = new myClass($args);
return self::$instance;
}
public function Get()
{
return self::$instance;
}
}
//index.php
<?php
require_once('myClass.php');
$instance = myClass::Create($args);
?>
Test Me!
//test.php
echo(is_null(myClass::Get())); //displays 1
So the problem is that from test.php, myClass::get() always returns null!
I have also tried to store the instance in the $_SESSION, which gives me the same result. Can you please point me in the right direction?

Answer 1

You should include file with the class difinition in each file where it used (and it should be included before it will in use).
<?php // filename: test.php
include_once("myClass.php");
$oClassInstance = myClass::Get();
var_dump($oClassInstance);
BTW
You don't need to define those two methods Create and Get. You can create only one method called getInstance:
// only one instance of the class
private static $_oInstance = null;
public static function getInstace()
{
if (!self::$_oInstance)
{
self::$_oInstance = new self();
}
return self::$_oInstance;
}
And then you can use it like:
<?php // filename: index.php
include_once("myClass.php");
// if instance does not exist yet then it will be created and returned
$oClass = myClass::getInstace();
<?php // filename: test.php
include_once("myClass.php");
// the instance already created and stored in myClass::$_oInstance variable
// so it just will be returned
$oClass = myClass::getInstance();
UPD
If you have to put some arguments into constructor just use predefined arguments:
private function __construct($aArg)
{
// this code will be launched once when instance is created
// in the any other cases you'll return already created object
}
public static function getInstance($aArgs = null)
{
if (!self::$_oInstance)
{
self::$_oInstance = new self($aArgs);
}
return self::$_oInstance;
}
ANSWER
Sorry that you have to scroll a few screens to find this =)))
The reason why you can't use myClass::Get() in you context is that you have 2 scripts that means - two different programs.
Singleton should be used within a single application (one script).
So in your case, correct usage will be module system:
- index.php
- main.php
- test.php
// file: index.php
include_once "myClass.php"
$module = $_GET["module"];
include_once $module ".php";
// file: main.php
$oClass = myClass::Create($someArgs);
var_dump($oClass); // you'll see you class body
// file: test.php
$oClass= myClass::Get();
var_dump($oClass); // you'll see the same class body as above
And your links will be:
index.php?module=main
index.php?module=test

Answer 2

The Create() function need to check whether $instance property already has a value before creating a new object. For example
public function Create()
{
if (is_null(self::$instance)) {
self::$instance = new self();
}
return self::$instance;
}
In test.php you can just call myClass::Create(), no need to have the Get() function at all