Design Patterns (singleton)

Singleton mode is the simplest design mode,

Intention:

Ensure that a class has only one instance and provides a global access point to access it.

Applicability:

There can only be one instance and the customer can access it from a well-known access point.

When this unique instance should be extensible by subclasses, and the customer should be able to use an extended instance without changing the code.

Schematic diagram:

Code implementation:

<?phpclass Singleton {//     private static $_instance = Array ();    private static $_instance = ";    Public $num = 0;    public static function getinstance () {        if (empty (self::$_instance)) {            self::$_instance = new self ();        }         if (Isset (self::$_instance[])) {//             self::$_instance = new self ();/         }        return self::$_instance;    } public        function sayname ($name = ' Zhangsan ') {        echo $name, "<br/>";        $this->num++;    }    Public Function Saynum () {        echo $this->num, "<br/>";    }}　　　　　　$test 1 = singleton::getinstance (); $test 1->sayname ();　　　　　　 Zhangsn$test1->saynum ();　　1$test2 = Singleton::getinstance (); $test 2->sayname (' Lisi ');　　　　　　Lisi$test2->saynum (); 2

　　

Design Patterns (singleton)