PHP single sample mode and factory mode Learning Summary-php Tutorial

PHP single sample mode and factory mode learning summary & lt ;? Php Singleton mode ** centralized control of database connection responsibilities * declares a singleton class * classDatabase {private $ _ db; declare a private instance variable (when constructing an object, the value of this variable will be summarized by the single-instance mode and factory mode in PHP.

 _ Db = pg_connect ('dbname = example_db ');} // declares the private _ clone method. in order to eliminate a vulnerability in php that can copy objects to undermine a single responsibility, private _ clone () {};/*** declare the getInstance () static method (constructed in Singleton mode). This method checks whether the static instance variable has saved an instance of this class. * If it does not contain an instance, the class will be initialized and saved to the $ _ instance variable. * When you access this code next time, the $ _ instance variable will save an instance of the class and the instance will not be initialized again. Finally, this method returns the instance reference */public static function getInstance () {if (! (Self: $ _ instance instanceof self) {self: $ _ instance = new self ();} return self ::$ _ instance ;} public function query ($ SQL) {return pg_query ($ this-> _ db, $ SQL ); // use $ this-> _ db to execute a query}/*** to use the singleton class */$ db = Database: getInstance (); $ db-> query ('select * from example_table '); /*** use a pure static class that cannot be instantiated */class SomeClass {// prevent the class from being treated as an instance using private function _ construct () {} public static function SomeMethod () {// perform some operations }}/////////// //////////////////////////////////////// ///// Factory mode: contains a class specifically used to create other objects. /*** Create a basic factory class */class MyObject {// The object will return from the factory} class MyFactory {public static function factory () {// return object return new MyObject () ;}// call method $ instance = MyFactory: factory (); //////////////////////////////////////// /// Image Object Factory/*** use factory class to parse image files */interface IImage {function getHeight (); function getWidth (); function getData ();} class Iamge_PNG implements IImage {private $ _ width, $ _ height, $ _ data; public function _ Construct ($ file) {$ this-> _ file = $ _ file; $ this-> _ parse ();} private function _ parse () {// Complete formatting and parsing // fill in $ _ width, $ _ height, $ _ data} public function getWidth () {return $ this-> $ _ width ;} public function getHeight () {return $ this-> $ _ height;} public function getData () {return $ this-> $ _ data ;}} class Iamge_JPEG implements IImage {private $ _ width, $ _ height, $ _ data; public function _ construct ($ file) {$ this-> _ file = $ _ file; $ This-> _ parse ();} private function _ parse () {// Complete formatting and parsing // fill in $ _ width, $ _ height, $ _ data} public function getWidth () {return $ this-> $ _ width;} public function getHeight () {return $ this-> $ _ height ;} public function getData () {return $ this-> $ _ data;} class ImageFactory {public static function factory ($ file) {$ pathParts = pathInfo ($ file ); switch (strtolower ($ pathParts ['extension']) {case 'jpg ': $ ret = new Image_J PEG ($ file); break; case 'PNG ': $ ret = new Image_PNG ($ file); break; case 'GIF': $ ret = new Image_GIF ($ file ); break; default; // PROBLEM} if ($ ret instanceof IImage) {return $ ret;} else {// problem }}// $ image = ImageFactory :: factory ('/path/to/my.jpg'); // $ image is now an example of the Image_JPEG class echo $ image-> getWidth (); /*** portable database × use the factory class to solve the database portability problem. */Interface IDatabaseBindings {public function userExists ($ email);} class PGSQL implements IDatabaseBindings {protected $ _ connection; public function _ construct () {$ this-> $ _ connection = pg_connect ('dbname = example_db ');} public function userExists ($ email) {$ emailEscaped = pg_escape_string ($ email ); $ query = 'SELECT 1 from users where email = "'. $ emailEscaped. '"'; if ($ result = pg_query ($ query, $ this-> $ _ Connection) {return (pg_num_row ($ result> 0 ))? True: false;} else {return false ;}} class MYSQL implements IDatabaseBindings () {protected $ _ connection; public function _ construct () {$ this-> $ connection = mysql_connect ('localhost'); mysql_select_db ('example _ db', $ this-> $ _ connection);} public function userExists ($ email) {$ emailEscaped = mysql_real_escape_string ($ email); $ query = 'SELECT 1 from users where email = "'. $ emailEscaped. '"'; if ($ result = m Ysql_query ($ query, $ this-> $ _ connection) {return (mysql_num_rows ($ result)> 0 )? True: false;} else {return false ;}} class DatabaseFactory {public static function factory () {$ type = loadtypefromconfigfile (); switch ($ type) {case 'pgsql': return new PGSQL (); break; case 'mysql': return new MYSQL (); break ;}}// usage $ db = DatabaseFactory :: factory (); $ db-> userExists ([email protected] ');?>