Comments on: PHP Singletons, Sub-Classing, and HAS-A Relationships http://www.justincarmony.com/blog/2008/12/03/php-singletons-sub-classing-and-has-a-relationships/ Web Designer & Software Engineer Tue, 15 May 2012 02:22:31 +0000 hourly 1 http://wordpress.org/?v=3.3.2 By: Justin Carmony http://www.justincarmony.com/blog/2008/12/03/php-singletons-sub-classing-and-has-a-relationships/comment-page-1/#comment-9747 Justin Carmony Tue, 16 Dec 2008 14:20:42 +0000 http://www.justincarmony.com/blog/?p=298#comment-9747 Thanks for the question Timmy. The reason for "static private $_instance" is for several reasons. First, I declare it static so that the variable is the same across any and all instances of this class. It is important because I use a static method to retrieve this value. Static methods do not have access to "$this". Second, the private is to ensure that the only manipulation done to the $_instance variable is by the CurrentUser class. By declaring it private, only functions withint the CurrentUser class have access to it. Outside I couldn't do "CurrentUser::$_instance;" to retrieve the object. You only can access it through the GetInstance function. This helps safe-guard against developers on accidentally breaking functionality. I hope this helps. Thanks for the question Timmy.

The reason for “static private $_instance” is for several reasons.

First, I declare it static so that the variable is the same across any and all instances of this class. It is important because I use a static method to retrieve this value. Static methods do not have access to “$this”.

Second, the private is to ensure that the only manipulation done to the $_instance variable is by the CurrentUser class. By declaring it private, only functions withint the CurrentUser class have access to it. Outside I couldn’t do “CurrentUser::$_instance;” to retrieve the object. You only can access it through the GetInstance function. This helps safe-guard against developers on accidentally breaking functionality.

I hope this helps.

]]> By: Timmy http://www.justincarmony.com/blog/2008/12/03/php-singletons-sub-classing-and-has-a-relationships/comment-page-1/#comment-9743 Timmy Tue, 16 Dec 2008 11:03:57 +0000 http://www.justincarmony.com/blog/?p=298#comment-9743 I dont think that "static private $_instance = null;" is good idea. Why is private for, if you could access from outside, like self::$_instance? It's not private then. Why you are not using $_instance variable as static in your GetInstance function? I dont think that “static private $_instance = null;” is good idea. Why is private for, if you could access from outside, like self::$_instance? It’s not private then. Why you are not using $_instance variable as static in your GetInstance function?

]]> By: Ross Scrivener http://www.justincarmony.com/blog/2008/12/03/php-singletons-sub-classing-and-has-a-relationships/comment-page-1/#comment-9413 Ross Scrivener Wed, 03 Dec 2008 08:16:17 +0000 http://www.justincarmony.com/blog/?p=298#comment-9413 Good stuff! Well written up, I've used a "registry" class in the past so I could store all kinds of data in one class rather than have lots of classes that effectively do nothing, but I guess both methods have their plus points. Good stuff! Well written up, I’ve used a “registry” class in the past so I could store all kinds of data in one class rather than have lots of classes that effectively do nothing, but I guess both methods have their plus points.

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