php Singleton 转自php手册

<?php
abstract class Singleton {
   protected function __construct() {
   }
   final public static function getInstance() {
       static $aoInstance = array();
       $calledClassName = get_called_class();
       if (! isset ($aoInstance[$calledClassName])) {
           $aoInstance[$calledClassName] = new $calledClassName();
       }
       return $aoInstance[$calledClassName];
   }
   final private function __clone() {
   }
}
class DatabaseConnection extends Singleton {
   protected $connection;
   protected function __construct() {
       // @todo Connect to the database
   }
   public function __destruct() {
       // @todo Drop the connection to the database
   }
}
$oDbConn = new DatabaseConnection();  // Fatal error
$oDbConn = DatabaseConnection::getInstance();  // Returns single instance
?>

重要的函数

get_called_class();

Gets the name of the class the static method is called in.