Review PHP设计模式之——注册模式

注册模式：

 class DbConnections{
     var $_store = array();
     public function isValid($key) {
         return isset($this->_store[$key]);
     }

     public function &get($key){
         if (isset($this->_store[$key]))
             return $this->_store[$key];
     }

     public function set($key, & $obj) {
         $this->_store[$key] = & $obj;
     }

     public function &getInstance(){
         static $instance = array();
         if (!$instance)
             $instance[0] = & new DbConnections;
         return $instance[0];
     }
 }

 class MysqlConnection{
     public $name = false;
     public function __construct($db){
         $this->name = $db;
         echo $db, "\n";
     }

     public function append($str){
         $this->name .= " ".$str;
     }
 }

 //initial setup, somewhere near the start of your script
 $dbc = & DbConnections::getInstance();
 $dbc->set('server1', new MysqlConnection('db1'));
 $dbc->set('server2', new MysqlConnection('db2'));
 $dbc->set('server3', new MysqlConnection('db3'));

 $dbc1 = $dbc->get('server1');
 $dbc2 = $dbc->get('server2');
 $dbc3 = $dbc->get('server3');

 $dbc1->append("connection");

 var_dump($dbc->get('server1'));
 var_dump($dbc->get('server2'));
 var_dump($dbc->get('server3'));