PDO未捕获的异常

Question

执行代码以下时，会出现此错误：

Fatal error: Uncaught exception 'PDOException' with message 
  'SQLSTATE[42000]: Syntax error or access violation: 1065 Query was empty'
  in /home/content/63/6563663/html/inventory/pg.php:20
Stack trace:
  #0 /home/content/63/6563663/html/inventory/pg.php(20): PDOStatement->execute()
  #1 {main} thrown in /home/content/63/6563663/html/inventory/pg.php on line 20

<?php

$u=$_GET["u"];


if ((isset($_POST["MM_update"])) && ($_POST["MM_update"] == "form2")) {
$amount = isset($_POST['amount']) ? $_POST['amount'] : null;
if (null != $amount) {

$user = 'username';
$pass = 'password';
$pdo = new PDO('mysql:host=localhost', $user, $pass);
$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
session_start();
$tablename = $_SESSION['MM_Username'];
$query = sprintf("UPDATE `%s` SET `stock` = :amount WHERE `itemname` = :u ", $tablename);
$stmt = $pdo->prepare($query);
$stmt->bindParam('amount', $amount);
$stmt->execute();
}
}

?>

作品但现在，此错误。我很抱歉，因为我是新来的PDO。

Fatal error: Uncaught exception 'PDOException' with message
  'SQLSTATE[HY093]: Invalid parameter number: number of bound variables does not match number of tokens'
  in /home/content/63/6563663/html/inventory/pg.php:20
Stack trace:
  #0 /home/content/63/6563663/html/inventory/pg.php(20): PDOStatement->execute()
  #1 {main} thrown in /home/content/63/6563663/html/inventory/pg.php on line 20

Answer 1

您或许应该熟悉trying和catching 例外的。

Answer 2

那么，该错误消息是相当清楚的：

  

1065查询是空

要使用的变量$UpdateQuery，它不存在。你大概的意思是说

 $stmt = $pdo->prepare($query);