一个比较常用的关于php下的mysql数据操作类

<?php
/*************************************************************
MySql类封装：
首先连接数据库，需要有参数
参数如何传？
    1、可以用配置文件
    2、可以通过构造函数传参
**************************************************************/
class SqlHelper{
    private $host;
    private $user;
    private $pwd;
    private $dbName;
    private $charset;
    private $conn = null; //保存连接资源

    public function __construct(){
        $this->host  = 'localhost';
        $this->user = 'xuwm';
        $this->pwd = 'bW7LA2pMDAEtnVB7';
        $this->dbName = 'gamejj';
        $this->charset='utf8';
        //连接
        $this->connect($this->host, $this->user, $this->pwd);
        //选库
        $this->switchDb($this->dbName);
        //设置字符集
        $this->setChar($this->charset);
    }

    //负责连接
    private function connect($host, $user, $pwd){
        $conn = mysql_connect($host, $user, $pwd);
         if (!$conn) {
            echo "Unable to connect to DB: " . mysql_error();
            exit;
        }
        $this->conn = $conn;
    }

    //选库
    public function switchDb($db){
        $sql = 'use ' . $db; //注意user 和 ' 有一个空格
        $this->query($sql);
    }

    //设置字符集
    public function setChar($char){
        $sql = 'set names ' . $char;
        $this->query($sql);
    }

    //关闭连接
    public function close(){
        mysql_close($this->conn);
    }

    //负责发送sql查询
    public  function query($sql){
        $result = mysql_query($sql, $this->conn);
        return $result;
    }

    //获取多行多列的select结果
    public function getAll($sql){
        $list  = array();
        $result = $this->query($sql);
        if(!$result)
            return false;
        while($row= mysql_fetch_assoc($result)){
            $list[] = $row;
        }
        return $list;
    }

    //获取一行数据 常用于 聚合函数
    public function getRow($sql){
        $result = $this->query($sql);
        if(!$result)
            return false;
        $row= mysql_fetch_assoc($result);
        return $row;
    }

     //获取一个值
    public function getOne($sql){
        $result = $this->query($sql);
        if(!$result)
            return false;
        $row= mysql_fetch_row($result);
        return $row[0];
    }

}

//$mysql = new SqlHelper();
/*
var_dump($mysql);
$sql = "insert goods values(1121, 4, '苹果')";
$mysql->query($sql);

$sql = 'select * from goods';
$list = $mysql->getAll($sql);
var_dump($list);

$sql = 'select * from goods where goods_id=4';
$list = $mysql->getRow($sql);
var_dump($list);

$sql = 'select count(*) from goods';
$list = $mysql->getOne($sql);
var_dump($list);
*/