note 65352 added to language.oop5.patterns

I don't agree to take a class with only static members and static methods as a 'singleton'. According to GoF's book, the singleton pattern means a class that only have one instance. A class containing only static members and functions still can be instantiated and extended, it have multiple instances. Consider the code below: <?php class StaticTest { private static $_test = "aaa"; public static function test() { echo self::$_test; } } $obj = new StaticTest(); ?> The code will not report errors(although it's useless). So there can be many instances of the class. It's reasonable that there is a class that create and store a unique instance of another class. Such as: <?php class A { private $_id = 0; public function getId() { return $this->_id; } } class B { private static $_instance; public static function singleton() { if (!isset(self::$_instance)) { self::$instance = new A(); } return self::$instance; } } ?> Here class B act as a guard to class A. But as same as the first section, it's useless too! Unless you can make sure that the users of your class will never find the class A, you shouldn't make the class you wanna to be unique can be instantiated many times. So the best way to create a unique instance of a class is that the class save the unique instance itself. It is the core meaning of singleton pattern. Any information that mentioned here can be found in the book of GoF. I think it's worth reading the book. BTW: It's allowed that there are a few of subclasses of a singleton class. ---- Server IP: 66.163.161.117 Probable Submitter: 219.142.118.227 ---- X-Spam-Status: No, hits=3.1 required=5.0 tests=DATE_MISSING,FROM_NO_LOWER autolearn=no version=2.64 ---- Manual Page -- http://www.php.net/manual/en/language.oop5.patterns.php Edit -- http://master.php.net/note/edit/65352 Del: integrated -- http://master.php.net/note/delete/65352/integrated Del: useless -- http://master.php.net/note/delete/65352/useless Del: bad code -- http://master.php.net/note/delete/65352/bad+code Del: spam -- http://master.php.net/note/delete/65352/spam Del: non-english -- http://master.php.net/note/delete/65352/non-english Del: in docs -- http://master.php.net/note/delete/65352/in+docs Del: other reasons-- http://master.php.net/note/delete/65352 Reject -- http://master.php.net/note/reject/65352 Search -- http://master.php.net/manage/user-notes.php