PHP patterns (factory & Singleton)

Factory

Definition:

<? PHP  Class  Example {  //  The factory Method      Public   Static   Function Factory ( $ Type  ){  If ( Include_once 'Drivers /'. $ Type . '. Php' ){ $ Classname = 'Driver _'. $ Type  ;  Return   New   $ Classname  ;}  Else  {  Throw   New   Exception ('Driver not found' );}}} ?>

Usage:

<?PHP//Load a MySQL driver$ Mysql= Example: Factory ('mysql');//Load a SQLite driver$ SQLite= Example: Factory ('sqlite');?>
 

 

 

Singleton

Definition:

<? PHP  Class  Example {  //  Hold an instance of the class      Private  Static   $ Instance  ;  //  A private constructor; prevents direct creation of Object      Private   Function  _ Construct (){  Echo 'I am constructed' ;}  //  The Singleton Method      Public   Static   Function Singleton (){  If (! Isset (SELF :: $ Instance  )){  $ C = _ Class __  ; Self :: $ Instance = New   $ C  ;}  Return SELF :: $ Instance ;}  //  Example Method      Public   Function  Bark (){  Echo 'Woof! ' ;}  //  Prevent users to clone the instance      Public   Function  _ Clone (){  Trigger_error ('Clone is not allowed .',E_user_error  );}} ?>

Usage:

 
   php  ///   This wocould fail because the constructor is private   $ test  =  New   example;  ///   This will always retrieve a singl E instance of the class   $ test  = example:  Singleton ();   $ test ->  bark ();   //   This will issue an e_user_error.   $ test_clone  =  clone  ( $ test  ); ?>