為什么此表達式的值為true？

Question

我正在使用php登錄功能，遇到了問題。 在腳本的一部分中，我正在測試是否所有信息都以html形式插入，並通過$ _POST變量提供給腳本。 並且在一部分中，腳本會正確評估是否僅輸入用戶名或僅輸入密碼，並且當我輸入正確的用戶名/密碼時，它將正確評估密碼是否錯誤，但是會激活錯誤“未輸入用戶名和密碼”。 我不知道。 FLASE && FALSE是否可能等於TRUE？

---編輯----好的，我現在看到我應該在此問題中包括所有相關文件。 因此，它們是：

index.php

<?php
session_start();
if (isset($_SESSION['login_message'])) {
    $message = $_SESSION['login_message'];
    unset($_SESSION['login_message']);
}
?>

<html>

<head>
<?php
require_once("include/head.php");
?>
</head>

<body>

<form action="auth/login.php" method="post">

<table>

<tr>

<td>
<img src="graphics/znak_hrz.png" alt="Znak HRZ" style="height: 200px; padding: 10px;">
</td>

<td>
    <table style="padding: 10px;">
            <tr>
                <td><?php if (isset($message)) {echo "<td>" . $message . "</td>";}?></td>
            </tr>

            <tr>
               <td>
               <label for="username">Username:</label>
               <input id="username" type="text" name="username" />
             </td>
            </tr>

            <tr>
              <td>
              <label for="password">Password:</label>
              <input id="password" type="password" name="password" />
              </td>
            </tr>

    <tr>
            <td style="text-align: center;">
            <input type="submit" name="login" value="Login" />
            </td>
    </tr>

    </table>
</td>

<td>
<img src="graphics/znak_eskadrile.png" alt="Znak eskadrile" style="height: 200px; padding: 10px;">
</td>

</tr>

</table>

</form>

</body>

</html>

login.php

<?php
session_start();

// This script will deny access if following conditions are met in that order:
// - Username not entered
// - Password not entered
// - Username and password not entered
// - User doesn't exist in the database
// - User is deactivated in the database
// - The password is wrong
// Upon successful login, it will redirect user to secure/index.php and
// upon unsuccessful login it will return him to index.php for another try.

// If username is not set, set an error message
if (empty($_POST['username']) && !empty($_POST['password'])) {
    $_SESSION['login_message'] = "Username missing";
}

// If password is not set, set an error message
if (empty($_POST['password']) && !empty($_POST['username'])) {
    $_SESSION['login_message'] = "Password missing.";
}

//If username AND password are not set, set an error message
if (empty($_POST['username']) && empty($_POST['password'])) {
    $_SESSION['login_message'] = "Username and password empty.";
}

// Check if the username exists in the database and if the password is correct
if (!isset($_SESSION['login_message']) && !empty($_POST['username']) && !empty($_POST['password'])) {

    require_once("database.php");

    // Sanitize incoming username and password
    $username = filter_var($_POST['username'], FILTER_SANITIZE_STRING);
    $password = filter_var($_POST['password'], FILTER_SANITIZE_STRING);

    // Determine whether an account exists matching this username and password
    $stmt = $auth_db->prepare("SELECT uid, pid, password, access_category, last_log, active FROM " . TBL_USERS . " WHERE username = ?");

    // Bind the input parameters to the prepared statement
    $stmt->bind_param('s', $username);

    // Execute the query
    $stmt->execute();

    // Assign results of query to temporary variables
    $stmt->bind_result($uid, $pid, $db_password, $access_category, $last_log, $active);
    $stmt->fetch();

        // If user doesn't exist in the database, deny login
        if (!isset($uid)) {
            $_SESSION['login_message'] = "User doesn't exist.";
        }

        // If user is deactivated, deny login
        if (isset($uid) && !$active) {
            $_SESSION['login_message'] = "User is deactivated.";
        }

        // If the password is wrong, deny login
        if (isset($uid) && $active && $db_password != md5($password)) {
            $_SESSION['login_message'] = "Wrong password.";
        }

        if (!isset($_SESSION['login_message'])) {

        // Close previous statement
        $stmt->close();

        // Update the account's last_login column
        $stmt = $auth_db->prepare("UPDATE " . TBL_USERS . " SET last_log = NOW() WHERE username = ?");
        var_dump($stmt);
        $stmt->bind_param('s', $username);
        $stmt->execute();

        // Set session variable
        $_SESSION['username'] = $username;
        $_SESSION['uid'] = $uid;
                $_SESSION['pid'] = $pid;
        $_SESSION['last_log'] = $last_log;
                $_SESSION['active'] = $active;
        $_SESSION['access_category'] = $access_category;
        }
}

if (!isset($_SESSION['login_message'])) {
    header('Location: ../secure/index.php');
} else if (isset($_SESSION['login_message'])) {
    header('Location: ../index.php');
}
?>

安全/ index.php

<?php
    session_start();
    require_once("../auth/login.php");
?>

<html>

<head>
<?php
#if($_SESSION['access_category'] == '0') {
#   header('Location: eth93sl/');
#}
?>
</head>

<body>
<?php
    echo "uid:" . $_SESSION['uid'] . "<BR>";
    echo "username: " . $_SESSION['username'] . "<BR>";
    echo "active: " . $_SESSION['active'] . "<BR>";
    echo "last_log: " . $_SESSION['last_log'] . "<BR>";
    echo "access_category: " . $_SESSION['access_category'] . "<BR>";
?>
</body>

</html>

Answer 1

問題是由於secure / index.php中的第三行，login.php腳本執行了兩次，這是我正在嘗試的另一個登錄系統的剩余行。 第二次調用該腳本時，它沒有$ _POST數據，因此沒有用戶名和密碼，因此激活了適當的條件。

提醒我，當我遇到問題時，也最好將我的觀點擴大到其他文件。

為什么此表達式的值為true？

問題描述

1 個解決方案

解決方案1
0 已采納 2014-08-07 10:21:30

為什么此表達式的值為true？

問題描述

1 個解決方案

解決方案1 0 已采納 2014-08-07 10:21:30

解決方案1
0 已采納 2014-08-07 10:21:30