新手/简单的php+mysql的面向对象 增删改查

<?php


class ryan_mysqli extends mysqli {
    public function __construct($host, $user, $pass, $db) {
        parent::__construct($host, $user, $pass, $db);


        if (mysqli_connect_error()) {
            die('Connect Error (' . mysqli_connect_errno() . ') '
                    . mysqli_connect_error());
        }
    }

public function names (){
$setnames="set names utf8";
$this->query($setnames);
}

public function insert($table,$id,$name,$sex,$phone){
$sql = "insert into $table values ($id,'$name','$sex',$phone)";
echo "$sql";
$result = $this->query ($sql);
if($result)
echo "add successfully";
else
echo "add failed";

}

public function delete($table,$id){
$sql = "delete from $table where id=$id";
echo "$sql";
$result = $this->query ($sql);
if($result)
echo "deleted successfully";
else
echo "delete fail";
}


public function update($table,$name,$id){
$sql = "update $table set name='$name' where id=$id";
echo "$sql";
$result = $this->query ($sql);
if($result)
echo "update successfully";
else
echo "delete failed";
}


public function select ($table){
//$setnames="set names utf8";
//$this->query($setnames);
$charset = $this->character_set_name();
printf ("Current character set is %s", $charset);
$sql = "select * from $table";
echo "$sql";
$result = $this->query ($sql);
 
}


}

$db = new ryan_mysqli('localhost', 'root', '', 'stu_system');
$db->names();
//$db->insert ('users',32,'song','m',180);
//$db->delete('users',32);
//$db->update('users','yan',32);
$db->select('users');
$db->close();

?>

抛砖引玉，希望大神指导。