What's wrong in this singleton class - php

Question

I've 3 classes. [1]Singleton [2]Load [3]Dashboard . In Load class there is one method called 'model()'. Where i'm initializing data for singleton object by using this code.
$obj = Singleton::getInstance();
$obj->insertData('email', 'mail#domain.com');
Again, from Dashboard class there is one method called 'show()' from where i'm trying to print the Singleton object data. But, here i can see all the data of Singleton object except the data which has been initialized by 'model' method of 'Load' class.
Here is my full code...
<?php
//---Singletone Class---
class Singleton
{
// A static property to hold the single instance of the class
private static $instance;
// The constructor is private so that outside code cannot instantiate
public function __construct() {
if(isset(self::$instance))
foreach(self::$instance as $key => &$val)
{
$this->{$key} = &$val;
}
}
// All code that needs to get and instance of the class should call
// this function like so: $db = Database::getInstance();
public static function getInstance()
{
// If there is no instance, create one
if (!isset(self::$instance)) {
$c = __CLASS__;
self::$instance = new $c;
}
return self::$instance;
}
// Block the clone method
private function __clone() {}
// Function for inserting data to object
public function insertData($param, $element)
{
$this->{$param} = $element;
}
}
//---LOAD class---
class Load
{
function __construct()
{
$obj = Singleton::getInstance();
$obj->insertData('country', 'INDIA');
}
function model()
{
$this->name = 'Suresh';
$obj = Singleton::getInstance();
$obj->insertData('email', 'mail#domain.com');
}
function msg()
{
return('<br><br>This message is from LOAD class');
}
}
$obj = Singleton::getInstance();
$load = new load();
$obj->load = $load;
//---Dashboard Class---
class Dashboard extends Singleton
{
function __construct()
{
parent::__construct();
}
function show()
{
echo "Default data in current Object";
echo "<br>";
print_r($this);
echo $this->load->msg();
$this->load->model();
echo "<br><br>Data in current Object after post intialization";
echo "<br>";
print_r($this);
}
}
$dashboard = new dashboard();
$dashboard->show();

Answer 1

If your singleton was truly a singleton then the update would have worked. I'm suspecting that you may have multiple instances of the singleton class that is initialized.
Edit:
Also its not a good idea to inherit from a true singleton class.
You need to remove the inheritance that Dashboard has on Singleton
Edit:
Best practice on PHP singleton classes

Answer 2

I don't like your direct access to an object like an array. This one is a better approach [see here]:
You should call it like this:
$obj = Singleton::getInstance();
$load = new Load();
$obj->insertData( 'load', $load );
Implementation of Singleton:
class Singleton
{
// A static property to hold the single instance of the class
private static $instance;
// my local data
protected $_properties;
// You might want to move setter/getter to the end of the class file
public function __set( $name, $value )
{
$this->_properties[ $name ] = $value;
}
public function __get( $name )
{
if ( ! isset( $this->_properties[ $name ] )) {
return null;
}
return $this->_properties[ $name ];
}
// No need to check, if single instance exists!
// __construct can only be called, if an instance of Singleton actually exists
private function __construct() {
$this->_properties = array();
foreach(self::$instance as $key => &$val)
{
$this->_properties{$key} = &$val;
}
}
public static function getInstance()
{
if (!isset(self::$instance)) {
$c = __CLASS__;
self::$instance = new $c;
}
return self::$instance;
}
// Function for inserting data to object
public function insertData($param, $element)
{
$this->_properties{$param} = $element;
}
// Block the clone method
private function __clone() {}
}