$ stmt-> close()与$ stmt-> free_result() [英] $stmt->close() vs $stmt->free_result()

问题描述

在试图完成准备好的 mysqli 时，我试图弄清 $ stmt-> close()和 $ stmt-> free_result()之间的区别. strong>声明.

I am trying to clarify the difference between $stmt->close() and $stmt->free_result() when finalizing a prepared mysqli statement.

到目前为止，我使用:

$mysqli = new mysqli(host,user,password,database);
$stmt = $mysqli->prepare(sql statement);
[...]
$stmt->free_result();
$mysqli->close();

一切似乎都很好.

但是我已经看到很多程序员使用$ stmt-> close代替$ stmt-> free_result().并且一旦我看到了他们两个:

But I've seen a lot of programmers use $stmt->close instead of $stmt->free_result(). And once I've seen both of them:

$stmt->free_result();
$stmt->close();
$mysqli->close();

那我应该选择什么，在什么情况下以及为什么?

So what should I choose, under which circumstances and why?

推荐答案

$stmt->free_result()释放与结果集相关的内存，而$stmt->close()释放与已准备好的语句相关的内存.随后调用$stmt->close()将取消仍保留的任何结果.

$stmt->free_result() frees up memory related to a result set, whereas $stmt->close() frees up memory related to a prepared statement. Subsequently calling $stmt->close() will cancel any result still remaining.

本质上，调用$stmt->close()将提供与调用$stmt->free_result()相同的效果，因为它也会取消结果集.但是，调用$stmt->free_result()不会清除准备好的语句使用的内存，在这种情况下，您必须使用$stmt->close().

In essence, calling $stmt->close() will provide the same effect as calling $stmt->free_result() since it cancels the result set as well. But calling $stmt->free_result() will not clear out the memory used by the prepared statement in which case you must use $stmt->close().

要使用哪一个-在某些情况下，您打算使用已初始化的准备好的语句，但不再需要当前使用的结果集.在这种情况下，您将等待调用$stmt->close()直到完成准备好的语句，然后在执行另一条语句之前调用$stmt->free_result().

As far as which one to use goes - there may be situations where you intend on using the prepared statement you have initialized, but are no longer in need of the result set you currently have. In such a case you would wait on calling $stmt->close() until you are done with the prepared statement and instead call $stmt->free_result() before executing another statement.

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