刚转学php，请大家帮我写段数据库查询类的代码
大家好，本人初转php，想建立一个pdo连接的数据库操作类，但是不知道php的调用方法，请大家指点下。
类文件coon.php内容：
<?phpclass my_sql{public $dbh;public $sth;//连接数据库public function sql_open(){ $host='localhost'; //数据库主机名 $dbName='lif2'; //使用的数据库 $user='root'; //数据库连接用户名 $pass='123456'; //对应的密码 $dsn='mysql:host='.$host.';dbname='.$dbName; try { $dbh = new PDO($dsn, $user, $pass); $dbh->query("SET NAMES UTF8"); $dbh->exec("SET NAMES UTF8"); } catch(Exception $e) { echo 'data error: '.$e->getMessage(); }}//关闭数据库连接public function sql_close(){ $dbh=null;}//查询数据库public function my_query($sql){ $this->sql_open(); //$this->sth = $this->dbh->query($sql); //$result = $this->sth->fetchAll(); //return $result; 这里面怎么写才能返回数据？ }}?>页面调用代码：
<body><?phpinclude 'conn.php';$mysql = new my_sql;foreach ($mysql->my_query('SELECT * FROM user_type order by user_id') as $row){//这里循环输出查询内容}$mysql->sql_close();?></body>望详细指点下，实在弄不明白，用asp或asp.net的函数调用方法全不行，我想写一个查询，插入，更新和删除数据的通用函数，外部只要带入sql语句就可以执行的那种。
回复讨论(解决方案)
1楼围观。等大神解答！
$this->dbh = new PDO($dsn, $user, $pass);
你的my_query看上去没错，将注释的那几行打开。先试试看。
终于搞定了，看了网上众多代码，测试失败了无数次，结果是弄出来了，插入，删除，更新的通用类，请大神指点下这样做有没有什么弊端，会不会影响性能等。下一步研究下那个参数化，据说可以防止sql注入。
conn.php内容：
<?php//数据库操作类class my_sql{public $user='root'; //数据库连接用户名public $pass='123456'; //对应的密码public $dsn='mysql:host=localhost;dbname=lif2';//查询数据库返回结果public function sql_select($sql){ try { $dbh = new PDO($this->dsn, $this->user,$this->pass); $dbh->query("SET NAMES UTF8"); return $dbh->query($sql); $dbh=null; } catch(Exception $e) { echo 'error: '.$e->getMessage(); }}//操作单条数据(更新/删除/插入)，无返回结果public function sql_one($sql){ try { $dbh = new PDO($this->dsn, $this->user,$this->pass); $dbh->exec("SET NAMES UTF8"); $dbh->exec($sql); $dbh=null; } catch(Exception $e) { echo 'error: '.$e->getMessage(); }}//操作多条数据（更新/删除），无返回结果public function sql_more($sql,$str){ try { $dbh = new PDO($this->dsn, $this->user,$this->pass); $dbh->exec("SET NAMES UTF8"); foreach($str as $arrs) { $dbh->exec($sql.$arrs); } $dbh=null; } catch(Exception $e) { echo 'error: '.$e->getMessage(); } }}?>页面调用函数：
include 'conn.php';$mysql = new my_sql;//操作单挑数据$mysql->sql_one("DELETE FROM `user_type` WHERE `user_id` = ".$_REQUEST['id']."");//读取内容$aa=$mysql->sql_select('SELECT * FROM user_type order by user_id'); foreach ($aa as $row) {//输出内容echo '<tr>';echo '<td>'.$row['user_id'].'</td><td>'.$row['user_name'].'</td><td>'.$row['user_real_name'].'</td><td>'.$row['user_sex'].'</td><td>'.$row['user_tel'].'</td><td>'.$row['user_qq'].'</td><td>'.$row['user_address'].'</td><td>'.$row['user_email'].'</td><td><a href="?action=del&id='.$row['user_id'].'" title="删除">删除</a></td><td><input name="delAll[]" class="c" type="checkbox" value="'.$row['user_id'].'" /></td>';echo '</tr>';}//操作多条数据$id=$_POST['delAll'];if(isset($id)){$mysql->sql_more("DELETE FROM `user_type` WHERE `user_id` = ",$id);}上面的操作方法和思路还是沿袭了asp.net开发的习惯，不知道在php开发上实用不，望大神指点一下。
你现在这个不能防注入，防注入需要用PDO::prepare
<?php/* Execute a prepared statement by passing an array of values */$sth = $dbh->prepare('SELECT name, colour, calories FROM fruit WHERE calories < ? AND colour = ?');$sth->execute(array(150, 'red'));$red = $sth->fetchAll();$sth->execute(array(175, 'yellow'));$yellow = $sth->fetchAll();?> 你现在这个不能防注入，防注入需要用PDO::prepare
<?php/* Execute a prepared statement by passing an array of values */$sth = $dbh->prepare('SELECT name, colour, calories FROM fruit WHERE calories < ? AND colour = ?');$sth->execute(array(150, 'red'));$red = $sth->fetchAll();$sth->execute(array(175, 'yellow'));$yellow = $sth->fetchAll();?>你说的这个方法我已经会弄了，参数化查询
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