数据库类 的 封装

<?php
class db{
private $host;
private $username;
private $password;
private $db_name;
private $link;
public function __construct($host,$username,$password,$db_name){
$this->host=$host;
$this->username=$username;
$this->password=$password;
$this->db_name=$db_name;
$this->connect();
}
private function connect(){
mysql_connect($this->host,$this->username,$this->password);
mysql_select_db($this->db_name);
mysql_query('set names utf8');
}
public function get_All($db_name){
$sql="select * from $db_name";
$res=mysql_query($sql);
$array=array();
while($row=mysql_fetch_array($res)){
$array[]=$row;
}
return $array;
}
public function get_one_row($db_name){
$sql="select * from $db_name";
$res=mysql_query($sql);
$row=mysql_fetch_row($res);
return $row;
}
public function get_one_assoc($db_name){
$sql="select * from $db_name";
$res=mysql_query($sql);
$row=mysql_fetch_assoc($res);
return $row;
}
}
?>