希望我的用户能够更改用户密码

我的网站上有一个允许用户更改密码的页面

表单要求用户名，当前密码，新密码，确认新密码。

如果用户输入了所有信息，会弹出一个脚本，请正确填写表单

和错误信息显示

(注意:未定义变量:wtbusers in/home/www/hostname/dr/filename第16行

警告:mysql_num_rows():提供的参数不是一个有效的MySQL结果资源在/home/www/hostname/dr/filename(第20行)

我的代码粘贴在下面，如果有人可以帮助，这将是非常感激!谢谢!

蒂娜

修改密码信息界面:

<div id="inlogscherm">
<form name="form1" method="post" action="changepw.php">
    <div class="textm">Change password</div><br>
    <div class="text">Username:</div><div class="invulbalkje"><? echo "{$_SESSION['username']}"; ?></div><br />
    <input name="username" type="text" id="username" value="<? echo "{$_SESSION['username']}"; ?>">
  <div class="text">Password:</div><input name="pin" type="password" id="pin" class="invulbalkje"><br />
    <div class="text">New Password:</div><input name="newpassword" type="password" id="newpassword" class="invulbalkje"><br />
    <div class="text">Repeat New Password:</div><input name="repeatnewpassword" type="password" id="repeatnewpassword" class="invulbalkje"><br />
    <input type="submit" name="Submit" value="Change" class="button">
</form>

(changepw.php)

<?php 
error_reporting(E_ALL);
ini_set('display_errors', 1);
session_start();
include 'db.php';

$username = $_POST['username'];
$pin = $_POST['pin'];
$newpassword = $_POST['newpassword'];
$repeatnewpassword = $_POST['repeatnewpassword'];
$encrypted_password=md5($pin);
$encrypted_newpassword=md5($newpassword);
$result = mysql_query("SELECT pin FROM $wtbusers WHERE  username='$username' and pin = '$pin'");
if(!$result) 
{ 
echo"<script>alert('Please Fill Form Correctly')</script>"; } 
if(mysql_num_rows($result)){
if($newpassword==$repeatnewpassword){
    $sql=mysql_query("UPDATE $wtbusers SET pin='$pin' where   username='$username'");        
    if($sql) 
    { 
            header("location:success.php");
    }
    else
    {
       header("location:error3.php");
    }       
} else {
    header("location:error_password_not_matched.php");
}
} else {
echo"<script>alert('Please Fill Form Correctly')</script>"; 
}
?> 

如果你看到问题请联系我。我会非常感激你的!

error_reporting(E_ALL);
ini_set('display_errors', 1);
session_start();
include 'db.php';
// print_r($_POST);
if (isset($_POST['username'])) {
    $username = $_POST['username'];
}
if (isset($_POST['pin'])) {
    $pin = $_POST['pin'];
}
if (isset($_POST['newpassword'])) {
    $newpassword = $_POST['newpassword'];
}
if (isset($_POST['repeatnewpassword'])) {
    $repeatnewpassword = $_POST['repeatnewpassword'];
}
$encrypted_password = md5($pin);
$encrypted_newpassword = md5($newpassword);
$wtbusers = '`users`'; //this should be defined (change this to your whatever table name)
$result = mysql_query("SELECT pin FROM $wtbusers WHERE  username='$username' and pin = '$pin'");
if (!$result) {
    echo "<script>alert('Please Fill Form Correctly')</script>";
}
if (mysql_num_rows($result) != 0) {
    if ($newpassword == $repeatnewpassword) {
        $sql = mysql_query("UPDATE $wtbusers SET pin='$pin' where   username='$username'");
        if ($sql) {
            header("location:success.php");
        }
        else {
            header("location:error3.php");
        }
    }
    else {
        header("location:error_password_not_matched.php");
    }
}
else {
    echo "<script>alert('Please Fill Form Correctly')</script>";
}