php - 嵌套 PDO 查询失败？

Question

我有以下代码:

$sql = $pdo->query("SELECT pageid FROM webpages WHERE ISNULL(deleted) ORDER BY sortindex"); 
while ($row = $sql->fetch(PDO::FETCH_ASSOC)) {
  switch ($row["pageid"]) {
  case "information":
    Write("  <li class='top'><a href='index.php?m=info' id='info' class='top_link'><span class='down'>Information</span></a>");
    Write("    <ul class='sub'>");
    Write("      <li><a href='index.php?m=info&submode=n'>News</a></li>");
    Write("      <li><a href='index.php?m=info&submode=e'>Events</a></li>");
    Write("      <li><a href='index.php?m=info&submode=m'>Minutes</a></li>");
    $subsql = $pdo->query("SELECT * FROM categories WHERE visible = 1 ORDER BY sortindex,category"); 
    while ($catrow = $subsql->fetch(PDO::FETCH_ASSOC)) Write("      <li><a href='index.php?m=info&cat={$catrow["cid"]}'>{$catrow["category"]}</a></li>");
    Write("    </ul>");
    break;
  }
}

当我运行它时，我收到“ fatal error :在第 29 行对/chroot/home/web/html/test.php 中的非对象调用成员函数 fetch()”，第 29 行是“while ($catrow..."行。

但在我的开发服务器上，它可以工作。我应该检查什么来弄清楚如何使其在生产服务器上工作？我不知道为什么它会失败。如果我将代码移出第一个 SQL 循环，它在生产中可以正常工作。这没问题:

$sql = $pdo->query("SELECT pageid FROM webpages WHERE ISNULL(deleted) ORDER BY sortindex"); 
while ($row = $sql->fetch(PDO::FETCH_ASSOC)) {
  switch ($row["pageid"]) {
  case "information":
    Write("  <li class='top'><a href='index.php?m=info' id='info' class='top_link'><span class='down'>Information</span></a>");
    Write("    <ul class='sub'>");
    Write("      <li><a href='index.php?m=info&submode=n'>News</a></li>");
    Write("      <li><a href='index.php?m=info&submode=e'>Events</a></li>");
    Write("      <li><a href='index.php?m=info&submode=m'>Minutes</a></li>");
    Write("    </ul>");
    break;
  }
}
$subsql = $pdo->query("SELECT * FROM categories WHERE visible = 1 ORDER BY sortindex,category"); 
while ($catrow = $subsql->fetch(PDO::FETCH_ASSOC)) Write("Cat: {$catrow["category"]}<br/>");

当我运行它时，第一个循环运行，然后我就得到了类别列表。我知道我无法通过 Stack Overflow 来对我的服务器进行故障排除，但如果有人知道哪种配置调整或其他问题会导致这种行为，我将非常感谢任何提示:)

Answer 1

未完全获取的语句可能会阻止其他语句实际发生(因此 $subsql 不是有效的 PDO 对象)。这可能有效:

$rows = $pdo->query("SELECT pageid FROM webpages WHERE ISNULL(deleted) ORDER BY sortindex")->fetchAll(PDO::FETCH_ASSOC); 
foreach ($rows as $row) {
  switch ($row["pageid"]) {
  case "information":
    Write("  <li class='top'><a href='index.php?m=info' id='info' class='top_link'><span class='down'>Information</span></a>");
    Write("    <ul class='sub'>");
    Write("      <li><a href='index.php?m=info&submode=n'>News</a></li>");
    Write("      <li><a href='index.php?m=info&submode=e'>Events</a></li>");
    Write("      <li><a href='index.php?m=info&submode=m'>Minutes</a></li>");
    $subsql = $pdo->query("SELECT * FROM categories WHERE visible = 1 ORDER BY sortindex,category"); 
    while ($catrow = $subsql->fetch(PDO::FETCH_ASSOC)) Write("      <li><a href='index.php?m=info&cat={$catrow["cid"]}'>{$catrow["category"]}</a></li>");
    Write("    </ul>");
    break;
  }
}