Application Analysis of single-case and multi-case design patterns in php design patterns

This article gives a detailed analysis of the single-case and multi-case application in the php design mode. For more information, see Singleton) the pattern and the uncommon Multiton pattern control the number of classes in the application. For example, the mode name can only be instantiated once for a single instance and only one object. the mode can be instantiated multiple times.

Based on the Singleton feature, we often use Singleton to configure the application and define variables that may be accessed at any time in the application. But sometimes Singleton is not recommended because it generates a global state and

This single root object does not encapsulate any system functions. In most cases, unit testing and debugging are difficult. The reader decides based on the actual situation.
Sample code:
The code is as follows:
Class SingletonExample {
Private function _ construct () {}// prevents direct instantiation
Public static function getInstance () {// not associated with any object
Static $ instance = null; // all code that calls this function shares this variable, so it is not necessary to make it a static variable of the class.
If ($ instance = null ){
$ Instance = new SingletonExample ();
}
Return $ instance;
}
}
$ Obj1 = SingletonExample: getInstance ();
$ Obj2 = SingletonExample: getInstance ();
Var_dump ($ obj1 ===$ obj2); // true is the same instance.
?>

Multiton is similar to singleton. The difference is that the latter requires the getInstance () function to pass key values.
For a given key value, only a unique object instance exists. if multiple nodes exist, each node has a unique table identifier, in addition, each node may appear multiple times in a single execution (such as a node in cms), so you can use the Multiton mode to implement these nodes. the Multiton mode saves memory, make sure that multiple instances of the same object do not conflict.
Example:
The code is as follows:
Class MultitonExample {
Private function _ construct () {}// prevents direct instantiation

Public static function getInstance ($ key ){
Static $ instance = array ();
If (! Array_key_exists ($ key, $ instance )){
$ Instance [$ key] = new SingletonExample ();
}
Return $ instance ($ key );
}
};
?>