how to check if object of a class already exists in PHP?

Question

consider the following code scenario:

<?php //widgetfactory.class.php // define a class class WidgetFactory { var $oink = 'moo'; } ?> <?php //this is index.php include_once('widgetfactory.class.php'); // create a new object //before creating object make sure that it already doesn't exist if(!isset($WF)) { $WF = new WidgetFactory(); } ?>

The widgetfactory class is in widgetfactoryclass.php file, I have included this file in my index.php file, all my site actions runs through index.php, i.e. for each action this file gets included, now I want to create object of widgetfactory class ONLY if already it doesn't exist. I am using isset() for this purpose, is there any other better alternative for this?

This is a 'singleton': php.net/manual/en/language.oop5.patterns.php (see example #2) — Marc B
– Marc B, Commented Apr 5, 2012 at 21:16
@j08691 I guess class_exist() wont help this case, as I want to check wheather the object exists or not and not the class — Rahul
– Rahul, Commented Apr 5, 2012 at 21:20
Could be helpful php.net/manual/en/language.oop5.patterns.php — The Alpha
– The Alpha, Commented Apr 5, 2012 at 21:21
I am now looking for almost exactly the same thing. Anyone any more recent methods for achieving this? — Mm-Art-In
– Mm-Art-In, Commented Dec 15, 2015 at 15:51

Linus Kleen · Accepted Answer · 2012-04-05 21:18:28Z

Using globals might be a way to achieve this. The common way to do this are singleton instances:

class WidgetFactory { private static $instance = NULL; static public function getInstance() { if (self::$instance === NULL) self::$instance = new WidgetFactory(); return self::$instance; } /* * Protected CTOR */ protected function __construct() { } }

Then, later on, instead of checking for a global variable $WF, you can retrieve the instance like this:

$WF = WidgetFactory::getInstance();

The constructor of WidgetFactory is declared protected to ensure instances can only be created by WidgetFactory itself.

Mahdi · Accepted Answer · 2017-01-11 10:37:13Z

5

This should do the job:

if ( ($obj instanceof MyClass) != true ) { $obj = new MyClass(); }

edited Jan 11, 2017 at 10:37

answered Sep 11, 2012 at 8:39

Mahdi

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