class MysqlClient {
   protected $_database = '';      // 数据库名
   protected $_hostname = '';      // host
   protected $_hostport = '';      // 端口
   protected $_username = '';      // 数据库密码
   protected $_password = '';      // 数据库用户名
   protected $_pconnect = '';      // 常连接
   protected $_query = null;       // 常连接
   protected $_connection = null;  // 创建的连接

   protected $_table = '';         // 表名
   public  $_column = array();

   /**
    * 构造函数，完成配置和数据连接
    * @param array $config
    * @throws Exception
    * @return
    */
   public function __construct(array $config = null) {
       if (null === $config) {
           return false;
       }
       $index = mt_rand(0, count($config['hostname']) -1);

       $this->_database = $config['database'];
       $this->_hostname = $config['hostname'][$index];
       $this->_hostport = $config['hostport'];
       $this->_username = $config['username'];
       $this->_password = $config['password'];
       $this->_pconnect = $config['pconnect'];
       $this->connect();
   }

   /**
    * 数据库连接
    * @throws Exception
    * @return unknown
    */
   public function connect() {
       $this->_start = microtime(true);
       $func = $this->_pconnect ? 'mysql_pconnect' : 'mysqli';
       $connection = new  mysqli($this->_hostname, $this->_username, $this->_password, $this->_database, $this->_hostport);
       if ( $connection -> connect_error ) {
           return;
       }
       else {
           $this->_connection = $connection;
           $this->query('set names utf8;');
       }
   }

   /**
    * @return
    */
   public function error() {
       return mysqli_error($this->_connection);
   }

   /**
    * 数据库重连接
    * Enter description here ...
    * @return
    */
   public function reconnect() {
       if (false === @mysqli_ping($this->_connection)) {
           mysqli_close($this->_connection);
           return $this->connect();
       }
       return $this->_connection;
   }

   /**
    * sql的增删改查
    * @param unknown_type $sql
    * @param unknown_type $type
    * @throws Exception
    * @return unknown
    */
   public function query($sql, $type = 'ASSOC') {
       if (false === ($this->_query = mysqli_query($this->_connection,$sql))) {
           $this->reconnect();
           if (false === ($this->_query = mysqli_query($this->_connection,$sql))) {
               $message = 'Invalid query: ' . $this->error();
               return -1;
           }
       }
       $tags = explode(' ', $sql, 2);
       switch (strtoupper($tags[0])) {
           case 'SELECT':
               ($result = $this->fetchAll($type)) || ($result = array());
               break;
           case 'INSERT':
           case 'REPLACE':
               $result = mysqli_insert_id($this->_connection);
               break;
           case 'UPDATE':
           case 'DELETE':
               $result = mysqli_affected_rows($this->_connection);
               break;
           default:
               $result = $this->_query;
       }
       return $result;
   }

   /**
    * 获取select结果
    * @param unknown_type $type
    * @return Ambigous <multitype:, unknown>
    */
   public function fetchAll($type = 'ASSOC') {
       switch ($type) {
           case 'ASSOC':
               $func = 'mysqli_fetch_assoc';
               break;
           case 'NUM':
               $func = 'mysqli_fetch_array';
               break;
           case 'OBJECT':
               $func = 'mysqli_fetch_object';
               break;
           default:
               $func = 'mysqli_fetch_assoc';
       }
       $result = array();
       while (false != ($row = $func($this->_query))) {
           $result[] = $row;
       }
       @mysqli_free_result($this->_query);
       return $result;
   }

   /**
    * @return
    * @param esc
    */
   public function real_escape_string($escapestr){
       return  $this->_connection->real_escape_string($escapestr);
   }
}