PHP design mode single-instance mode (single-element mode) _php Tutorial

PHP design mode singleton mode (single element mode)

Single-Case mode:

As an object's creation mode, Singleton mode ensures that a class has only one instance, and instantiates itself and provides this instance to the whole system globally. Instead of creating an instance copy, it returns a reference to the instance stored inside the singleton class.

(1). You need a static member variable that holds a unique instance of the class: private static $_instance;

(2). Constructors and clone functions must be declared private to prevent the external program new class from losing the meaning of the singleton pattern:

Private Function __construct () {$this->_db = pg_connect (' xxxx ');} Private Function __clone () {}

(3). You must provide a public static method that accesses this instance (typically the GetInstance method), which returns a reference to the unique instance:

public static function getinstance () {if (! (Self::$_instance instanceof Self)) {self::$_instance = new self ();} return self::$_instance;}

Why use PHP singleton mode?

1, the application of PHP is mainly in the database application, so there will be a large number of database operations in an application, using a singleton mode, you can avoid a large number of new operations to consume resources.

2, if the system needs to have a class to control some of the configuration information globally, then using the singleton mode can be easily implemented.

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