class HMongodb {   

  private $mongo;  //Mongodb连接
  private $curr_db_name;
  private $curr_table_name;
  private $error;   

  public function getInstance($mongo_server, $flag=array())
  {
    static $mongodb_arr;
    if (empty($flag['tag']))
    {
      $flag['tag'] = 'default';     }
    if (isset($flag['force']) && $flag['force'] == true)
    {
      $mongo = new HMongodb($mongo_server);
      if (empty($mongodb_arr[$flag['tag']])) 
      {
        $mongodb_arr[$flag['tag']] = $mongo;
      }
      return $mongo;
    }
    else if (isset($mongodb_arr[$flag['tag']]) && is_resource($mongodb_arr[$flag['tag']]))
    {
      return $mongodb_arr[$flag['tag']];
    }
    else
    {
      $mongo = new HMongodb($mongo_server);
      $mongodb_arr[$flag['tag']] = $mongo;
      return $mongo;
    }
  }

  /**
   * 构造函数
   * 支持传入多个mongo_server(1.一个出问题时连接其它的server 2.自动将查询均匀分发到不同server)
   *
   * 参数：
   * $mongo_server:数组或字符串-array("127.0.0.1:1111", "127.0.0.1:2222")-"127.0.0.1:1111"
   * $connect:初始化mongo对象时是否连接，默认连接
   * $auto_balance:是否自动做负载均衡，默认是
   *
   * 返回值：
   * 成功：mongo object
   * 失败：false
   */
  private function __construct($mongo_server, $connect=true, $auto_balance=true)
  {
   if (is_array($mongo_server))
   {
   $mongo_server_num = count($mongo_server);
   if ($mongo_server_num > 1 && $auto_balance)
   {
    $prior_server_num = rand(1, $mongo_server_num);
    $rand_keys = array_rand($mongo_server,$mongo_server_num);
    $mongo_server_str = $mongo_server[$prior_server_num-1];
    foreach ($rand_keys as $key)
    {
    if ($key != $prior_server_num - 1)
    {
     $mongo_server_str .= ',' . $mongo_server[$key];
    }
    }
   }
   else
   {
    $mongo_server_str = implode(',', $mongo_server);
   }         }
   else
   {
    $mongo_server_str = $mongo_server;
   }
   try {
    $this->mongo = new Mongo($mongo_server, array('connect'=>$connect));
   }
   catch (MongoConnectionException $e)
   {
    $this->error = $e->getMessage();
    return false;
   }
  }

  /**
  * 连接mongodb server
  *
  * 参数：无
  *
  * 返回值：
  * 成功：true
  * 失败：false
  */
  public function connect()
  {
    try {
      $this->mongo->connect();
      return true;
    }
    catch (MongoConnectionException $e)
    {
      $this->error = $e->getMessage();
      return false;
    }
  }   

  /**
  * select db
  *
  * 参数：$dbname
  *
  * 返回值：无
  */
  public function selectDb($dbname)
  {
    $this->curr_db_name = $dbname;
  }   

  /**
  * 创建索引：如索引已存在，则返回。
  *
  * 参数：
  * $table_name:表名
  * $index:索引-array("id"=>1)-在id字段建立升序索引
  * $index_param:其它条件-是否唯一索引等
  *
  * 返回值：
  * 成功：true
  * 失败：false
  */
  public function ensureIndex($table_name, $index, $index_param=array())
  {
    $dbname = $this->curr_db_name;
    $index_param['safe'] = 1;
    try {
      $this->mongo->$dbname->$table_name->ensureIndex($index, $index_param);
      return true;
    }
    catch (MongoCursorException $e)
    {
      $this->error = $e->getMessage();
      return false;
    }
  }

  /**
  * 插入记录
  *
  * 参数：
  * $table_name:表名
  * $record:记录
  *
  * 返回值：
  * 成功：true
  * 失败：false
  */
  public function insert($table_name, $record)
  {
    $dbname = $this->curr_db_name;
    try {
      $this->mongo->$dbname->$table_name->insert($record, array('safe'=>true));
      return true;
    }
    catch (MongoCursorException $e)
    {
      $this->error = $e->getMessage();
      return false;
    }
  }   

  /**
  * 查询表的记录数
  *
  * 参数：
  * $table_name:表名
  *
  * 返回值：表的记录数
  */
  public function count($table_name)
  {
    $dbname = $this->curr_db_name;
    return $this->mongo->$dbname->$table_name->count();
  }   

  /**
  * 更新记录
  *
  * 参数：
  * $table_name:表名
  * $condition:更新条件
  * $newdata:新的数据记录
  * $options:更新选择-upsert/multiple
  *
  * 返回值：
  * 成功：true
  * 失败：false
  */
  public function update($table_name, $condition, $newdata, $options=array())
  {
    $dbname = $this->curr_db_name;
    $options['safe'] = 1;
    if (!isset($options['multiple']))
    {
      $options['multiple'] = 0;     }
    try {
      $this->mongo->$dbname->$table_name->update($condition, $newdata, $options);
      return true;
    }
    catch (MongoCursorException $e)
    {
      $this->error = $e->getMessage();
      return false;
    }
  }   

  /**
  * 删除记录
  *
  * 参数：
  * $table_name:表名
  * $condition:删除条件
  * $options:删除选择-justOne
  *
  * 返回值：
  * 成功：true
  * 失败：false
  */
  public function remove($table_name, $condition, $options=array())
  {
    $dbname = $this->curr_db_name;
    $options['safe'] = 1;
    try {
      $this->mongo->$dbname->$table_name->remove($condition, $options);
      return true;
    }
    catch (MongoCursorException $e)
    {
      $this->error = $e->getMessage();
      return false;
  }  }   

  /**
  * 查找记录
  *
  * 参数：
  * $table_name:表名
  * $query_condition:字段查找条件
  * $result_condition:查询结果限制条件-limit/sort等
  * $fields:获取字段
  *
  * 返回值：
  * 成功：记录集
  * 失败：false
  */
  public function find($table_name, $query_condition, $result_condition=array(), $fields=array())
  {
    $dbname = $this->curr_db_name;
    $cursor = $this->mongo->$dbname->$table_name->find($query_condition, $fields);
    if (!empty($result_condition['start']))
    {
      $cursor->skip($result_condition['start']);
    }
    if (!empty($result_condition['limit']))
    {
      $cursor->limit($result_condition['limit']);
    }
    if (!empty($result_condition['sort']))
    {
      $cursor->sort($result_condition['sort']);
    }
    $result = array();
    try {
      while ($cursor->hasNext())
      {
        $result[] = $cursor->getNext();
      }
    }
    catch (MongoConnectionException $e)
    {
      $this->error = $e->getMessage();
      return false;
    }
    catch (MongoCursorTimeoutException $e)
    {
      $this->error = $e->getMessage();
      return false;
    }
    return $result;
  }   

  /**
  * 查找一条记录
  *
  * 参数：
  * $table_name:表名
  * $condition:查找条件
  * $fields:获取字段
  *
  * 返回值：
  * 成功：一条记录
  * 失败：false
  */
  public function findOne($table_name, $condition, $fields=array())
  {
    $dbname = $this->curr_db_name;
    return $this->mongo->$dbname->$table_name->findOne($condition, $fields);
  }   

  /**
  * 获取当前错误信息
  *
  * 参数：无
  *
  * 返回值：当前错误信息
  */
  public function getError()
  {
    return $this->error;
  }

  /*** Mongodb类** examples:
   * $mongo = new HMongodb("127.0.0.1:11223");
  * $mongo->selectDb("test_db");
  * 创建索引
  * $mongo->ensureIndex("test_table", array("id"=>1), array('unique'=>true));
  * 获取表的记录
  * $mongo->count("test_table");
  * 插入记录
  * $mongo->insert("test_table", array("id"=>2, "title"=>"asdqw"));
  * 更新记录
  * $mongo->update("test_table", array("id"=>1),array("id"=>1,"title"=>"bbb"));
  * 更新记录-存在时更新，不存在时添加-相当于set
  * $mongo->update("test_table", array("id"=>1),array("id"=>1,"title"=>"bbb"),array("upsert"=>1));
  * 查找记录
  * $mongo->find("c", array("title"=>"asdqw"), array("start"=>2,"limit"=>2,"sort"=>array("id"=>1)))
  * 查找一条记录
  * $mongo->findOne("$mongo->findOne("ttt", array("id"=>1))", array("id"=>1));
  * 删除记录
  * $mongo->remove("ttt", array("title"=>"bbb"));
  * 仅删除一条记录
  * $mongo->remove("ttt", array("title"=>"bbb"), array("justOne"=>1));
  * 获取Mongo操作的错误信息
  * $mongo->getError();
  */

}