Learn PHP design pattern singleton pattern
Release： 2016-07-25 09:05:17
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/** - * PHP design pattern singleton mode
- * $_instance must be declared as a static private variable
- * The constructor and destructor must be declared private to prevent external programs from creating new
- * classes and thereby losing the meaning of the singleton mode
- * getInstance The () method must be set to public, and this method must be called
- * to return a reference to the instance
- *:: The operator can only access static variables and static functions
- * new objects will consume memory
- * Usage scenarios: the most commonly used The place is the database connection.
- * After using the singleton pattern to generate an object,
- * the object can be used by many other objects.
- * @link http://bbs.it-home.org
- */
class Danli { - //Static member variables that save class instances
- private static $ _instance;
- //Construction method of private tag
- private function __construct(){
- echo 'This is a Constructed method;';
- }
-
- //Create __clone method to prevent the object from being copied and cloned
- public function __clone(){
- trigger_error('Clone is not allow!',E_USER_ERROR);
- }
//Single instance method, a public static method used to access the instance - public static function getInstance(){
- if(!(self::$_instance instanceof self)){
- self::$_instance = new self;
- }
return self::$_instance; - }
public function test(){ - echo 'Calling method successfully';
- }
- }
//Classes that use new to instantiate the private mark constructor will report an error - // $danli = new Danli();
- //The correct method is to use the double colon::operator to access the static method to obtain the instance
- $danli = Danli::getInstance();
- $danli->test();
- // Copying (cloning) the object will result in an E_USER_ERROR
- $danli_clone = clone $danli;
- ?>
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