php Singleton Database connection(单例)

<?php
abstract class UMA_Plugin_Mongo
{
    protected $name = null;
    private  $_db;
    //单例模式
 private static $_dbinstance;
    public static function getDbInstance()
    {
     if(self::$_dbinstance == null)
     {
      $_dbinstance = new iDatabase(IDATABASE_PROJECT_ID, IDATABASE_PASSWORD);
     }
     return $_dbinstance;
    }
    public function __construct () {
     
     $this->_db = $this->getDbInstance();//Zend_Registry::get('mongoDB');
    }
    
    public function getDB() {
     return $this->_db;
    }
    
    public function find($query=array(),$sort = array("_id"=>1),$skip=0,$limit=10000) {
     return $this->_db->find($this->name, $query, $sort, $skip, $limit);
    }
    
    public function findOne($query) {
     return $this->_db->findOne($this->name, $query);
    }
    
    public function findAndModify($options) {
     return $this->_db->findAndModify($this->name, $options);
    }
    
    public function count($query) {
     return $this->_db->count($this->name, $query);
    }
    
    public function remove($query) {
     return $this->_db->remove($this->name, $query);
    }
    
    public function insert ($object) {
     return $this->_db->insert($this->name, $object);
    }
    
    public function update ($criteria, $object)
    {
     return $this->_db->update($this->name, $criteria, $object);
    }
    
    public function aggregate(array $ops) {
     return $this->_db->aggregate($this->name, $ops);
    }
    
    public function getCondition($condition = null)
    {
     $query= array();
     if(!empty($condition)){
      foreach($condition as $k=>$v){
       if(!empty($v)){
        $query[$k] = trim($v);
       }
      }
     }      
     return $query;
    }
    
    /**
     * Load Smarty library
     */
    public static function LoadSmarty()
    {
     require_once(SMARTY_DIR.'Smarty.class.php');
     $smarty = new Smarty();
     $smarty->template_dir = BASE_DIR.'templates/';
     $smarty->compile_dir = BASE_DIR.'templates_c/';
     $smarty->left_delimiter = "{{";
     $smarty->right_delimiter = "}}";
     $smarty->allow_php_tag=true;
     return $smarty;
    }
    
    public static function LoadMySmarty()
    {
     require_once(SMARTY_DIR.'MySmarty.php');
     $mysmarty = new MySmarty();
     $mysmarty->template_dir = BASE_DIR.'templates/';
     $mysmarty->compile_dir = BASE_DIR.'templates_c/';
     $mysmarty->left_delimiter = "{{";
     $mysmarty->right_delimiter = "}}";
     $mysmarty->allow_php_tag=true;
     return $mysmarty;
    }
    
    public static  function LoadFront1126Smarty()
    {
     require_once(SMARTY_DIR.'Front1126Smarty.php');
     $mysmarty = new Front1126Smarty();
     $mysmarty->template_dir = BASE_DIR.'templates/';
     $mysmarty->compile_dir = BASE_DIR.'templates_c/';
     $mysmarty->left_delimiter = "{{";
     $mysmarty->right_delimiter = "}}";
     $mysmarty->allow_php_tag=true;
     return $mysmarty;
    }
    
    public static function LoadFrontSmarty()
    {
     require_once(SMARTY_DIR.'FrontSmarty.php');
     $fsmarty = new FrontSmarty();
     $fsmarty->template_dir = BASE_DIR.'templates/';
     $fsmarty->compile_dir = BASE_DIR.'templates_c/';
     $fsmarty->left_delimiter = "{{";
     $fsmarty->right_delimiter = "}}";
     $fsmarty->allow_php_tag=true;
     return $fsmarty;
    }
}


//--------------------------------------------------------
class ConnectionFactory
{
 　　private static $factory;
 　　public static function getFactory()
 　　{
  　　　　if(!self::$factory)
  　　　　self::$factory =new ConnectionFactory(...);
  　　　　return self::$factory;
　　 }
　　private $db;
　　public function getConnection()
　　{
　　　　if(!$db)
      　　$db =new PDO(...);
　　　　return $db;
　　}
}
//调用
function getSomething()
{
    　　$conn =ConnectionFactory::getFactory()->getConnection();...


//-----------------------------------------实例二------------------------------------------

class Database Singleton
{
  // [Singleton]
  private static $instance =null;
  public static function getInstance()
  {
    if(!self::$instance)
    {
      self::$instance =new self();
    }
    return self::$instance;
  }
  privatefunction __clone(){}
  // [/Singleton]

  private $connection =null;

  private function __construct()
  {
    $this->connection = mysql_connect('localhost','root','admin');
    if($this->connection)
    {
      mysql_select_db('my_database');
    }
  }

  //
  // crud operations go here.
  //
}

$db =DatabaseSingleton::getInstance();
$db->SomeCRUDOperation();

//----------------------------------实例三-------------------------------------

class Database
{
  private static $instance =null;

  private static $conn;

  private function __construct()
  {
    self::$conn =new mysqli('localhost','root','root','database','3307');
  }

  public static function getInstance()
  {
    if(self::$instance ==null){
      self::$instance =new Database();
    }

    return self::$instance;
  }

  public function query($sql)
  {
    return self::$conn->query($sql);
  }
}