PHP Design Patterns Singleton Pattern_PHP Tutorial

PHP design pattern singleton mode

　Singleton mode: Makes an object of a class the only instance in the system.

The most common use of singleton mode in PHP is database operations. To avoid having multiple database connection operations in the system and wasting system resources, you can use the singleton mode. One instance is used for each database operation.

　Simple example

　class AClass {

// Used to store your own instances

public static $instance;

// Private constructor to prevent external objects from instantiating objects

　private function __construct() {}

// Private clone function to prevent external objects from being cloned

private function __clone() {}

// Static method, singleton access unified entrance

public static function getInstance() {

　if (!(self::$instance instanceof self)){

Self::$instance = new self();

　}

return self::$instance;

　}

// test

public function test() {

return "done";

　}

// Private clone function to prevent external objects from being cloned

private function __clone() {}

　}

class BClass extends AClass{

　}

// Get instance

　$aclass = AClass::getInstance();

$bclass = BClass::getInstance();

// Call method

echo $aclass->test();

For some relatively large applications, multiple databases may be connected, so different databases sharing a common object may cause problems, such as the allocation of connection handles, etc. We can change $instance into an array and pass different Parameters to control

　Simple example

class DB {

// Used to store your own instances

public static $instance = array();

public $conn;

// Private constructor to prevent external objects from instantiating objects

private function __construct($host, $username, $password, $dbname, $port) {

$this->conn = new mysqli($host, $username, $password, $dbname, $port);

　}

// Static method, singleton access unified entrance

Public static function getInstance($host, $username, $password, $dbname, $port) {

$key = $host.":".$port;

　if (!(self::$instance[$key] instanceof self)){

Self::$instance[$key] = new self($host, $username, $password, $dbname, $port);#Instantiation

　}

return self::$instance[$key];

　}

//query

public function query($ql) {

return $this->conn->query($sql);

　}

// Private clone function to prevent external objects from being cloned

private function __clone() {}

// Release resources

public function __destruct(){

$this->conn->close();

　}

　}

http://www.bkjia.com/PHPjc/951489.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/951489.htmlTechArticle Singleton mode of PHP design pattern Singleton mode: makes an object of a class become the only instance in the system. PHP The most common use of singleton mode is database operations. Avoid being in the system...