PHP登录表单和注销按钮不能正常显示

Question

我刚开始学习PHP，并且在简单的登录页面工作时遇到了一些麻烦。当我第一次加载这个脚本时，文本“错误的密码/用户名”。并且注销按钮被打印，但不是登录表单。为什么会发生这种情况，以及如何更改代码以使登录表单和注销按钮按预期一起工作？

<?php 

if (isset($_POST['log_out'])) { // If the page was reloaded as a result of the user having clicked the logout button, 
session_destroy(); // kill session. 
} 

session_start(); // Start a new session with 

$_SESSION['user'] = 'foo'; // a static username, and 
$_SESSION['pass'] = 'bar'; // a static password. 
// If I insert $_SESSION['logged_in'] = 'false'; here to start things off, a blank alert box will be returned no matter from where on the page I alert() the value with JS. On the other hand, without this line the same alert will return "1" both here and further down in the script. 

if (($_POST['username'] == $_SESSION['user']) && ($_POST['password'] == $_SESSION['pass'])) { // If the username and password filled in before the page reload match the static ones, 
    $_SESSION['logged_in'] = true; // the user is logged in. 
} else { // If there is no match ... 
    echo 'Wrong password/username.'; 
} 

include("head.php"); // HTML snippet with everything from the DOCTYPE to the opening BODY tag. 

?> 
      <div> // HTML interlude ... 
<?php 

// If the user is logged in, print out a logout button in HTML at the top of the page: 

if (isset($_SESSION['logged_in']) && ($_SESSION['logged_in'] == true)) { 
    echo '   <form action="index.php" method="post">'; 
    echo '   <input type="submit" name="log_out" value="Log out">'; 
    echo '   </form>'; 
} 

?> 
       <p>HTML interlude ...</p> 

<?php 

// If the user is not logged in, print out a login form in HTML at the bottom of the page: 

if ($_SESSION['logged_in'] != true) { 

    echo '   <form action="index.php" method="post">'; 
    echo '    <label for="username">Username</label><br>'; 
    echo '    <input type="text" name="username" id="username"><br>'; 
    echo '    <label for="password">Password</label><br>'; 
    echo '    <input type="text" name="password" id="password"><br>'; 
    echo '    <input type="submit" name="submit" id="submit" value="Log in">'; 
    echo '   </form>'; 

} 

?> 
      </div> 
<?php include("footer.php"); ?> 

Answer 1

if (($_POST['username'] == $_SESSION['user']) && ($_POST['password'] == $_SESSION['pass'])) { the static ones, 
    $_SESSION['logged_in'] = true; // the user is logged in. 
} else { 
    echo 'Wrong password/username.'; 
} 

页面加载后的第一次，因为如果没有来自$_POST['username']病情会是假的这部分将显示“密码错误/用户名”。

将条件isset($_POST['username']) && isset($_POST['password'])添加到两个选项中。像这样：

if(isset($_POST['username']) && isset($_POST['password'])){ 
    if (($_POST['username'] == $_SESSION['user']) && ($_POST['password'] == $_SESSION['pass'])) { the static ones, 
     $_SESSION['logged_in'] = true; // the user is logged in. 
    } else { 
     echo 'Wrong password/username.'; 
    } 
} 

这种方式不会在第一次加载页面时评估，但只有在发布凭证时才会对此进行评估。

Answer 2

您可以通过调试脚本发现：商店的预期为变量，并打印出来，例如：

$isLoggedIn = $_SESSION['logged_in']; # Give things a name! (always useful) 
echo 'isLoggedIn: ', var_dump($isLoggedIn), "\n"; # debugging 
if ($isLoggedIn != true) { 

    echo '   <form action="index.php" method="post">'; 
    echo '    <label for="username">Username</label><br>'; 
    echo '    <input type="text" name="username" id="username"><br>'; 
    echo '    <label for="password">Password</label><br>'; 
    echo '    <input type="text" name="password" id="password"><br>'; 
    echo '    <input type="submit" name="submit" id="submit" value="Log in">'; 
    echo '   </form>'; 

} 

Answer 3

第一次加载你的页面，然后除非你传递所需的后变量，您的条件检查

if (($_POST['username'] == $_SESSION['user']) && ($_POST['password'] == $_SESSION['pass'])) 

将失败，因此显示Wrong password/username.消息。

Answer 4

代码看起来不错，实际上对于“刚刚学习”的人来说做得很好。

鉴于代码没有明显错误（几个粗糙的边缘 - 比较布尔值时应该考虑使用'==='而不是'=='），那么也许这就是会话问题。

尝试...

print_r（$ _ SESSION）;

after session_start（）;并在选择是否显示注销按钮的条件之前。

每当您不要将参数发布到页面以及发布错误值时，都会显示错误的用户名消息。试试这个：

if (($_POST['username']) 
    && ($_POST['username'] == $_SESSION['user']) 
    && ($_POST['password'] == $_SESSION['pass'])) { 

顺便说一下，这个会话不是存储用户名和密码的好储存库 - 它是特定于当前用户的。对于多用户系统，这些将存储在单独的数据库中，例如，

if (($_POST['username']) && lookup($_POST['username'], $_POST['password'])) { 
...