如果未设置语句对象，是否需要调用PDOStatement :: closeCursor()? [英] Is a call to PDOStatement::closeCursor() necessary if the statement object is unset anway?
问题描述
我正在将基于Mysql的 PDO连接与 PDOStatement (::prepare(); ::execute())结合使用，并且我已经处理了以前开发人员的一些代码，在方法中使用 PDOStatement::closeCursor() .
I'm utilizing a Mysql based PDO connection with PDOStatement (::prepare(); ::execute()) and I've run over some code from a previous developer that utilizes PDOStatement::closeCursor() in a method.
无论如何，该语句在函数末尾都未设置:
The statement is unset at the end of the function anyway:
public function fooBar($identifier)
{
...
/** @var $dbc PDO */
$dbc = $conn->getConnection();
$stmt = $dbc->prepare('SELECT orderType, orderComment, payload FROM cart WHERE identifier = :identifier');
$stmt->execute(array('identifier' => $identifier));
$stmt->setFetchMode(PDO::FETCH_OBJ);
$cart = $stmt->fetch();
$stmt->closeCursor();
...
return $result;
}
在我的心智模型中，我会说这里无论如何都清除了PDOStatement，因为我期望该对象负责此内务处理(封装基础知识).因此，对我来说，调用PDOStatement::closeCursor()似乎是多余的，因为这可能不完全是这里想要的:由于该语句不再被重复使用，因此我根本不需要关闭游标.
In my mental model, I'd say that the PDOStatement is cleared here anyway, as I exepect the object to take care of this housekeeping (encapsulation basics). Therefore calling PDOStatement::closeCursor() looks supferfluous to me, especially, as this might not be exactly what is wanted here: As the statement is not to be re-used, I don't need to close the cursor at all.
边注:该代码是示例性的，在实际代码中，如果行数不为一(1)，则甚至在
$stmt->execute(...)之后引发异常.
side-note: this code is exemplary, in the real code, there is even an exception thrown after
$stmt->execute(...)if the row-count is not one (1).
Stackoverflow上的现有材料
不是正义一些驱动程序-驱动程序提供的某些设置需要在触发另一个查询之前关闭结果集，例如关闭MySQL的
PDO::MYSQL_ATTR_USE_BUFFERED_QUERY.值得庆幸的是，您可以调用closeCursor，并且不需要采取任何措施时，它将成功执行任何操作.否则，只需取消设置包含语句句柄的变量即可清除.
Not just some drivers -- some settings provided by drivers require closing the result set before firing off another query, like turning off MySQL's
PDO::MYSQL_ATTR_USE_BUFFERED_QUERY. Thankfully you can callcloseCursorand it will successfully do nothing when it doesn't need to take action. Otherwise simply unsetting the variable containing the statement handle will clean up.
另一个问题何时应为PDO语句使用closeCursor()?没有被接受的答案，我不会怀疑关于，因为它们全都如鱼得水.
Another question When should I use closeCursor() for PDO statements? has no accepted answer which I don't wonder about because it's all wishy-washy.
在 重复使用PDO语句var会使进程崩溃 ，其中有
In Reusing PDO statement var crashes the process there is a comment made that unsetting a variable does not get all errors (memory corruption bugs) out of the way:
[...]我确实尝试在重新分配它之前取消设置var语句，但这没有帮助. [...]
[...] I did try to unset the statement var before reassigning it but it didn't help. [...]
但是我不知道对于范围将消失的局部变量来说是否也是如此.我也不使用mod_php作为SAPI.
However I don't know if this is also true for local variables whose scope is to be gone. I also don't use mod_php as SAPI.
推荐答案
相同的清除操作pdo_mysql_stmt_cursor_closer() ，因此只要显式未设置语句对象或超出范围，该操作将始终执行.
pdo_mysql_stmt_dtor() runs the same cleanup operations as pdo_mysql_stmt_cursor_closer(), so as long as the statement object is either explicitly unset or goes out of scope, the operations will always be performed.
因此，如果该语句无论如何都将被销毁，则不必严格地调用closeCursor().就个人而言，我还是会这样做，因为我希望明确易读，但这取决于个人的风格偏好.
It is therefore not strictly necessary to call closeCursor() if the statement is about to be destroyed anyway. Personally I would do it anyway as I like to be explicit for readability, but that comes down to personal stylistic preferences.
基于以上参考，只能肯定地说 关于PDO_mysql-对于其他驱动程序，可能不成立.
Based on the references above, this can only be said for certain about PDO_mysql - for other drivers this may not hold true.
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