问题描述
我正在重构一些旧代码，包括重写基本的 mysql 查询以使用 PDO.
I am refactoring some old code, including rewriting basic mysql queries to use PDO.
以下适用于所有浏览器和所有图像类型:
The following works brilliantly in all browsers and for all image types:
$query = 'SELECT image FROM image WHERE imageid=' . $image_id;
$result = mysql_query($query, $db_conn); querycheck($result);
header("Content-type: image");
echo mysql_result($result, 0);
不幸的是，尽管我使用 PDO 重写了它，但它不起作用.我已经浏览了整个 PDO 文档和标准的网络搜索，但没有任何建议/解决方案有效.
Unfortunately, however I rewrite it using PDO, it doesn't work. I've been through the entire PDO documentation and the standard web search, but none of the advice/solutions work.
如何使用 PDO 从 MySQL 中轻松获取图像并显示它?
How can one easily fetch and image from MySQL using PDO and display it?
编辑 1:
Matthew Ratzloff 给出了下面应该是显而易见的答案，但它不起作用.这是我使用 PDO 测试的实际代码(我尝试了许多变体/参数):
Matthew Ratzloff gives what should be the obvious answer below, but it does not work. Here is the actual code that I test using PDO (and I have tried many variants/parameters):
$connectstring_temp = 'mysql:host=' . $A . ';dbname=' .$B;
$dbh_temp = new PDO($connectstring_temp, $login, $password);
#$dbh_temp->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
#$dbh_temp->setAttribute(PDO::MYSQL_ATTR_USE_BUFFERED_QUERY,true);
$sql = "SELECT image FROM image WHERE imageid=" . $image_id;
$query = $dbh_temp->prepare($sql);
$query->execute();
$query->bindColumn(1, $image, PDO::PARAM_LOB);
$query->fetch(PDO::FETCH_BOUND);
header("Content-Type: image");
echo $image;
我保留了相同的语法，但最终代码 $image_id 需要作为参数传递.上面的代码不起作用.PDO 适用于所有类型的所有其他查询.
I've kept the same syntax, although for the final code $image_id needs to be passed as a parameter. The code above does NOT work. PDO works fine for all other queries of all types.
推荐答案
需要参数化imageid值并将参数绑定到PDO::PARAM_LOB:
You need to paramaterize the imageid value and bind the parameter to PDO::PARAM_LOB:
$sql = "SELECT image FROM image WHERE imageid=:id";
$query = $db_conn->prepare($sql);
$query->execute(array(':id' => $image_id));
$query->bindColumn(1, $image, PDO::PARAM_LOB);
$query->fetch(PDO::FETCH_BOUND);
header("Content-Type: image");
echo $image;
当然，您还需要指定完整、正确的内容类型(例如，图像/png).
Of course, you'll also want to specify the complete, correct content type (e.g., image/png).
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