PHP SQL While循环不工作

我有一个代码，它应该从

收藏夹

中获取用户的所有收藏夹，然后它应该使用该信息从

菜单

中获取信息，将它们显示为图片

它所要做的就是显示用户最喜欢的图片，但目前它只会显示一张图片，而他们最喜欢的图片有很多

<?php
$con=mysqli_connect("localhost","UN","PW","DB");

// Check connection
if (mysqli_connect_errno()) {
  echo "Failed to connect to MySQL: " . mysqli_connect_error();
}
$id=$_SESSION['user']['id'];
$result = mysqli_query($con,"SELECT * FROM favourites WHERE user='$id'");

while($row = mysqli_fetch_array($result)) {
    $code=$row['gamecode'];
    $con=mysqli_connect("localhost","UN","PW","DB");
    // Check connection
    if (mysqli_connect_errno()) {
        echo "Failed to connect to MySQL: " . mysqli_connect_error();
    }

    $result = mysqli_query($con,"SELECT * FROM menus WHERE code='$code'");

    while($row = mysqli_fetch_array($result)) {
?>
<a href="<?php echo $row['link']; ?>">
<img src="<?php echo $row['picture']; ?>" alt="<?php echo $row['game']; ?>"      height="120" width="150" class="fade"></a>
<?php
    }
    mysqli_close($con);
}

mysqli_close($con);

?>

---

通过重新连接到循环中的数据库，您正在终止查询

$con = mysqli_connect(...) // connection #1
$result = mysqli_query(...);
while($row = mysqli_fetch($result)) {
   $con = mysqli_connect(...); // connection #2

再次连接时，会终止原始连接，从而终止查询

除非您需要使用不同的凭据连接两次，否则不需要第二次连接。一个连接可以处理多个查询

顺便说一句，如果您使用了不同的连接句柄变量，例如

$con = mysqli_connect(...);
    $othercon = mysqli_connect(...);

你就不会有这个问题了。您可以有多个连接，但不能使用同一个变量。
请查看它是否可以使用不同的结果变量，而只能使用一个DB连接

<?php
$con=mysqli_connect("localhost","UN","PW","DB");
// Check connection
if (mysqli_connect_errno()) {  echo "Failed to connect to MySQL: " . mysqli_connect_error(); }
$id = $_SESSION['user']['id'];
$result1 = mysqli_query($con,"SELECT * FROM favourites WHERE user='$id'");
while($row = mysqli_fetch_array($result1)) {
    $result2 = mysqli_query($con,"SELECT * FROM menus WHERE code='".$row['gamecode']."");
    while($row2 = mysqli_fetch_array($result2)) { ?>
<a href="<?php echo $row2['link']; ?>">
<img src="<?php echo $row2['picture']; ?>" alt="<?php echo $row2['game']; ?>"      height="120" width="150" class="fade"></a>
<?php }
}
mysqli_close($con);
?>

您有两个MySQL连接，它们具有相同的变量名
$con
，以及
$result
和
$row
。所以我只需更改内部循环中的变量名，这样它们就不会冲突&所有这些都应该可以工作<代码>$con\u inside

，

$result\u inside

和

$row\u inside

我还添加了

或die（mysqli_error（））

到您的

mysqli\u查询

行，以便在查询终止时返回错误

<?php
$con = mysqli_connect("localhost","UN","PW","DB");

// Check connection
if (mysqli_connect_errno()) {
  echo "Failed to connect to MySQL: " . mysqli_connect_error();
}

$id = $_SESSION['user']['id'];

$result = mysqli_query($con, "SELECT * FROM favourites WHERE user='$id'") or die(mysqli_error());

while ($row = mysqli_fetch_array($result)) {

  $code = $row['gamecode'];

  $con_inside = mysqli_connect("localhost","UN","PW","DB");

  // Check connection
  if (mysqli_connect_errno()) {
    echo "Failed to connect to MySQL: " . mysqli_connect_error();
  }

  $result_inside = mysqli_query($con_inside, "SELECT * FROM menus WHERE code='$code'") or die(mysqli_error());

  while($row_inside = mysqli_fetch_array($result_inside)) {
?>

  <a href="<?php echo $row_inside['link']; ?>">
  <img src="<?php echo $row_inside['picture']; ?>" alt="<?php echo $row_inside['game']; ?>" height="120" width="150" class="fade"></a>

<?php
  }

  mysqli_close($con_inside);

}

mysqli_close($con);

---

为什么要在循环中多次连接到数据库？它们是两个不同的数据库。那么为什么要使用相同的变量？有两个数据库包含我试图获取的数据。这就是为什么有两个连接仍然没有必要。您可以非常轻松地执行

select db.table.field

。只需授予一个用户帐户对两个数据库的访问权限。那么，您必须为第二个连接使用其他变量名，您不能重复使用

result

和

row

@Bob是的，有两个连接。那很好。您只需要重命名连接句柄。请尝试我在回答中为您重新编写的代码。谢谢您的回答，但我刚刚尝试过，同样的事情也发生了。@Bob好的，现在再试一次。我还将一些

$row

变量更改为

$row\u inside

，这样内部连接结果就不会与主连接结果冲突。不幸的是，它仍然是一样的。@Bob现在再试一次。我还将

$result

调整为

$result\u-inside

。这样更好，非常感谢！

<?php

// Main DB connection.
$con = mysqli_connect("localhost","UN","PW","DB") or die(mysqli_connect_error());

// Inside DB connection.
$con_inside = mysqli_connect("localhost","UN","PW","DB") or die(mysqli_connect_error());

// Set the $id variable.
$id = $_SESSION['user']['id'];

// Set the query string.
$query = "SELECT * FROM favourites WHERE user='$id'";

// Bind the values to the query.
mysqli_stmt_bind_param($query, 's', $id);

// Get the result.
$result = mysqli_query($con, $query) or die(mysqli_error());

// Roll through the results.
while ($row = mysqli_fetch_array($result)) {

  // Set the $code variable.
  $code = $row['gamecode'];

  // Set the query string.
  $query_inside = "SELECT * FROM menus WHERE code='$code'";

  // Bind the values to the query.
  mysqli_stmt_bind_param($query_inside, 's', $code);

  // Get the result.
  $result_inside = mysqli_query($con_inside, $query_inside) or die(mysqli_error());

  // Roll through the results.
  while($row_inside = mysqli_fetch_array($result_inside)) {
?>

  <a href="<?php echo $row_inside['link']; ?>">
  <img src="<?php echo $row_inside['picture']; ?>" alt="<?php echo $row_inside['game']; ?>" height="120" width="150" class="fade"></a>

<?php
  }

  // Free the result set.
  mysqli_free_result($result_inside);

  // Close the connection.
  mysqli_close($con_inside);

}

// Free the result set.
mysqli_free_result($result);

// Close the connection.
mysqli_close($con);