Single-case mode of PHP design pattern (single element mode)

Single case mode:

As an object's creation pattern, the singleton pattern ensures that a class has only one instance, and instantiates it and provides it globally to the entire system. Instead of creating an instance copy, it returns a reference to an instance stored within a singleton class.

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

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

Private Function __construct ()

{

$this->_db = Pg_connect (' xxxx ');

}

Private Function __clone ()

{

}

(3). You must provide a public static method (usually the GetInstance method) to access this instance to return a reference to a unique instance:

public static function getinstance ()

{

if (! (Self::$_instance instanceof Self))

{

self::$_instance = new self ();

}

return self::$_instance;



}

Why use PHP as a single case mode?

1, the application of PHP is mainly in the database application, so an application will have a large number of database operations, the use of single case mode, you can avoid a large number of new operations to consume resources.

2, if the system needs to have a class to global control of some configuration information, then the use of a single example mode can be easily implemented.