为什么我的PHP登录脚本总是返回失败的登录？

Question

我无法弄清楚为什么mysql_num_rows($result)返回0，即使我插入的用户名和密码是正确的。我有一种感觉，我在代码中遗漏了一些明显的东西。

我经常被踢到登录失败页面。你能发现我的错误吗？ ：）

<?php
    // Start Session and Connect
    session_start();
    require_once('dbconnect.php');

    // Validation Errors
    $errmsg_arr = array();
    $errflag = false;

    // Connect to Database
    $link = mysql_connect(DB_HOST, DB_USER, DB_PASSWORD);
    if(!$link) {
        die('Failed to connect to server: ' . mysql_error());
    }

    $db = mysql_select_db(DB_DATABASE);
    if(!$db) {
        die("Unable to select database");
    }

    // Safety Goo.
    function clean($str) {
        $str = @trim($str);
        if(get_magic_quotes_gpc()) {
            $str = stripslashes($str);
        }
        return mysql_real_escape_string($str);
    }

    $login = clean($_POST['login']);
    $password = clean($_POST['password']);

    if($login == '') {
        $errmsg_arr[] = 'Login ID missing';
        $errflag = true;
    }
    if($password == '') {
        $errmsg_arr[] = 'Password missing';
        $errflag = true;
    }

    if($errflag) {
        $_SESSION['ERRMSG_ARR'] = $errmsg_arr;
        session_write_close();
        header("location: login.php");
        exit();
    }

        $qry="SELECT * FROM members WHERE login='$login' AND passwd='".md5($_POST['password'])."'";
    $result=mysql_query($qry);


    if($result) {
        if(mysql_num_rows($result) == 1) {
            //Login Successful
            session_regenerate_id();
            $member = mysql_fetch_assoc($result);
            $_SESSION['SESS_MEMBER_ID'] = $member['member_id'];
            $_SESSION['SESS_FIRST_NAME'] = $member['firstname'];
            $_SESSION['SESS_LAST_NAME'] = $member['lastname'];
            session_write_close();
            header("location: member-index.php");
            exit();
        }else {
            //Login failed
            header("location: login-failed.php");
            exit();
        }
    }else {
        die("Query failed");
    }
?>