PHP登錄表單和註銷按鈕不能正常顯示

Question

我剛開始學習PHP，並且在簡單的登錄頁面工作時遇到了一些麻煩。當我第一次加載這個腳本時，文本「錯誤的密碼/用戶名」。並且註銷按鈕被打印，但不是登錄表單。爲什麼會發生這種情況，以及如何更改代碼以使登錄表單和註銷按鈕按預期一起工作？

<?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.'; 
} 

頁面加載後的第一次，因爲如果沒有來自$_POST['username']病情會是假的這部分將顯示「密碼錯誤/用戶名」。

將條件isset($_POST['username']) && isset($_POST['password'])添加到兩個選項中。像這樣：

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.'; 
    } 
} 

這種方式不會在第一次加載頁面時評估，但只有在發佈憑證時纔會對此進行評估。

Answer 2

您可以通過調試腳本發現：商店的預期爲變量，並打印出來，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

第一次加載你的頁面，然後除非你傳遞所需的後變量，您的條件檢查

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

將失敗，因此顯示Wrong password/username.消息。

Answer 4

代碼看起來不錯，實際上對於「剛剛學習」的人來說做得很好。

鑑於代碼沒有明顯錯誤（幾個粗糙的邊緣 - 比較布爾值時應該考慮使用'==='而不是'=='），那麼也許這就是會話問題。

嘗試...

print_r（$ _ SESSION）;

after session_start（）;並在選擇是否顯示註銷按鈕的條件之前。

每當您不要將參數發佈到頁面以及發佈錯誤值時，都會顯示錯誤的用戶名消息。試試這個：

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

順便說一下，這個會話不是存儲用戶名和密碼的好儲存庫 - 它是特定於當前用戶的。對於多用戶系統，這些將存儲在單獨的數據庫中，例如，

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