用接口实现封装的一个mysqli工具类

<?php
   
   class DAOMysqli  implements I_Dao{

     //本类的对象实例
     private static $instance;
     //结果集
     private $result_row;
     //配置信息
     private $_host;
     private $_root;
     private $_dbname;
     private $_pw;
     private $_port;
     private $_charset;
    
    //mysqli实例化对象
     private $_mysqli;
     private function __construct($option){
       $this->_initArray($option);
       $this->_initMysqli();
     }
     private function __clone(){
     
     }
     //定义一个单例模式
     public static function getSingleton(array $option=array()){
      if(!(self::$instance instanceof self)){
         self::$instance =new self($option);
      }
         return self::$instance;
     }
     private function _initArray($option){
       $this->_host=isset($option['host'])?$option['host']:'';
       $this->_root=isset($option['root'])?$option['root']:'';
       $this->_dbname=isset($option['dbname'])?$option['dbname']:'';
       $this->_pw=isset($option['pw'])?$option['pw']:'';
       $this->_port=isset($option['port'])?$option['port']:'';
       $this->_charset=isset($option['charset'])?$option['charset']:'';
  
     }
     private function _initMysqli(){
      //实例化mysqli对象
      $this->_mysqli=new MYSQLI($this->_host,$this->_root,$this->_pw,$this->_dbname,$this->_port);
      if($this->_mysqli->connect_errno){
        echo "连接失败".$this->_mysqli->connect_error;
        exit;
       }
       //设置字符集编码
       $this->_mysqli->set_charset=$this->_charset;
     }
     //用于查询的方法
     public function query($sql=''){
      $result=$this->_mysqli->query($sql);
      if(false==$result){
        trigger_error("执行失败,你的sql语句有问题".$sql."错误消息".$this->_mysqli->error);
        return false;
      }
      $this->result_row=$result;
      return $result;
     }
     //用于非查询的方法
     public function execu($sql=''){
       $result=$this->query($sql);
       if(false==$result){
         return false;
       }else{
         echo "执行成功";
       }
     }
     //查询所有的记录
     public function fetchAll($sql=''){
      $result=$this->query($sql);
      if(false==$result){
       return false;
      }
      $rows=array();
      while($row=$result->fetch_array(MYSQLI_ASSOC)){
         $rows[]=$row;
      } 
       $result->free();
        return $rows;
     }
     //查询一条记录
     public function fetchRow($sql=''){
       $result=$this->query($sql);
       if(false==$result){
         return false;
       }
       $row=$result->fetch_array(MYSQLI_ASSOC);
       $result->free();
       return $row?$row:false;

     }
     //查询某条记录第一个字段
     public function fetchOne($sql=''){
       $result=$this->query($sql);
       if(false==$result){
         return false;
       }
       $row=$result->fetch_array(MYSQLI_NUM);
         $result->free();
       return $row?$row[0]:false;
     }
     //查询某个字段的所有记录
     public function fCoulumn($sql,$coulumn){
        $result=$this->fetchAll($sql);
        if(false==$result){
          return false;
        }
        $rows=array();
        foreach($result as $row){
        $rows[]=$row[$coulumn];
        }
        return $rows;
     }
     //用于提供转义的方法
     public function escapeData($data=''){
       
     }
     //获取被影响的记录数
     public function affectedRow(){
      $affected_row=$this->_mysqli->affected_rows;

      if($affected_row==0){
        echo "操作成功,但没有被影响";
      }
      return $affected_row;

     }
     //获取结果影响的记录数
     public function resultRow(){
      $num_rows=$this->result_row->num_rows; 
      $this->result=null;
      return $num_rows;
     

     }
     //获取最新自动生成的ID
     public function lastInsertId(){
       return $this->_mysqli->insert_id;
     }

   }
?>