header('Content-type:text/html;charset="utf-8"');

 class mysql{

     /*下面是私有字段*/

     private $host;      //表示mysql服务器

     private $user;      //表示用户名

     private $pass;      //表示密码

     private $database;  //表示数据库名

     private $charset;   //表示字符集

     /*私有方法：连接数据库*/

     private function _connect(){

         if(!mysql_connect($this->host,$this->user,$this->pass)){

             exit('连接数据库服务器失败！');

         }

         mysql_select_db($this->database);

         mysql_query("SET NAMES $this->charset");

     }

     /*析构方法:赋值给私有字段*/

     public function __construct($_host,$_user,$_pass,$_database,$_charset){

         $this->host= $_host;

         $this->user= $_user;

         $this->pass= $_pass;

         $this->database= $_database;

         $this->charset= $_charset;

         $this->_connect();

     }

     /*查询sql语句的方法*/

     public function select($sql,$table){

         $select = mysql_query("SELECT $sql From $table");

         return $select;

     }

     /*返回关联数组*/

     public function my_fetch_arr($_result,$result_type){

         $rows = mysql_fetch_array($_result,$result_type);

         return $rows;

     }

     /*插入sql语句的方法*/

     public function insert($table,$col,$value){

         if (!mysql_query("INSERT INTO $table($col)values($value)")){

             exit('插入数据时出现错误！');

         }

     }

     /*更新sql语句的方法*/

     public function update($table,$col,$new_value,$colm,$values){

         if (!mysql_query("UPDATE $table SET $col=$new_value where $colm=$values")){

             exit('更新数据时出现错误！');

         }

     }

     /*删除sql语句的方法*/

     public function delete($table,$col,$values){

         if (!mysql_query("DELETE FROM $table where $col=$values")){

             exit('删除数据时出现错误！');

         }

     }

     /*关闭连接方法*/

     public function _close(){

         mysql_close();

     }

 }

 //类的实例化，且运行了析构方法__construct();

 $mysql = new mysql("localhost","root","chang123","school","UTF8");  

 //执行了查询语句并将结果赋给$_result

 $_result = $mysql->select("*","grade");

 //返回从结果集中取的一行生成的关联数组或数字数组

 $rows = $mysql->my_fetch_arr($_result,MYSQL_ASSOC);

 //关闭数据库连接

 $mysql->_close();