插入到數據庫失敗，雖然預計要插入

Question

我想插入用戶和cursus id在數據庫中提交當前用戶定義在第二部分（請參閱評論）和數據庫連接是在在文件頂部需要一次。 當我現在按下按鈕它的迴應成功，但在數據庫記錄顯示。控制檯沒有顯示任何東西，當我回顯$ a或& b它給我正確的ID。我做錯了什麼？

<?php 
session_start(); 
require_once('includes/mysql_config.php'); 

//getting user data/id 
$id = isset($_SESSION['id']) ? $_SESSION['id'] : header('location: login.php'); 
$result = mysqli_query($con, "SELECT * FROM users WHERE id =".$_SESSION['id']); 
$user = mysqli_fetch_array($result); 
require_once('header.php'); 

$id = $_GET['id']; 
$result = mysqli_query($con, "SELECT * FROM cursus c LEFT OUTER JOIN cursussoort cr ON (c.cursussoort_ID = cr.id) WHERE c.ID = $id ORDER BY c.begindatum ASC"); 
$amount = mysqli_affected_rows($con); 

for ($i = 0; $i < $amount; $i++) { 
    $cursus = mysqli_fetch_array($result); 

$a = $cursus['id']; 
$b = $user['id']; 
//$a = mysqli_real_escape_string($a); 
//$b = mysqli_real_escape_string($b); 

    if(isset($_POST['submit'])){ 
     if($user['id']) { 
      $sql = "INSERT INTO aanmeldingen (users_id, cursus_id) VALUES ('$b', '$a')"; 
      $result = mysqli_query($sql); 
      echo "success"; 
     } else { 
      echo "failed"; 
     } 
    } 

?> 

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     <span class="sr-only">Toggle navigation</span> 
     <span class="icon-bar"></span> 
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     <span class="icon-bar"></span> 
     </button> 
     <!-- <a class="navbar-brand" href="index.html"> 
     <h1><img class="img-responsive" src="images/logo.png" alt="logo"></h1> 
     </a> --> 
    </div> 
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     <?php if(isset($_SESSION['id'])) { 
      echo '<li><a href="myaccount.php"><span>Mijn account</span></a></li>'; 
      echo '<li><a href="logout.php"><span>Log Out</span></a></li>'; 
     } else { 
      echo '<li><a href="login.php"><span>Log In</span></a></li>'; 
     } ?> 
     </ul> 
    </div> 
    </div> 
</div><!--/#main-nav--> 
<br><br> 
<!-- Post Content --> 
    <div class="container"> 
    <div class="row"> 
     <div class="col-lg-8 col-lg-offset-2 col-md-10 col-md-offset-1"> 
     <div class="col-lg-8 col-lg-offset-2 col-md-10 col-md-offset-1"> 
      <div class="post-preview"> 
      <h1> <?php echo $cursus['naam_cursus'] . "<br />";?></h1> 
      van: <?php echo $cursus['begindatum'] . "<br />";?> 
      tot: <?php echo $cursus['begindatum'] . "<br />";?> 
      <?php echo $cursus['beschrijving'] . "<br />";?> 
      </div> 
     </div> 
     </div> 
     <form method="post"> 
     <input type="submit" name="submit"> 
     </form> 
    </div> 
    </div> 
<?php } ?> 

<hr> 

如果你們需要更多的信息告訴我。

Answer 1

與您的代碼在這裏：

$result = mysqli_query($sql); 

mysqli_query（）需要兩個參數;連接和查詢。嘗試與此更換是，並告訴我，如果它固定您的問題：

$result = mysqli_query($con, $sql); 

馬特