(PHP 5 >= 5.1.0, PECL pdo >= 0.9.0)
PDOStatement::closeCursor — 关闭游标，使语句能再次被执行。
PDOStatement::closeCursor() 释放到数据库服务的连接，以便发出其他 SQL 语句，但使语句处于一个可以被再次执行的状态。
当上一个执行的 PDOStatement 对象仍有未取行时，此方法对那些不支持再执行一个 PDOStatement 对象的数据库驱动非常有用。 如果数据库驱动受此限制，则可能出现失序错误的问题。
PDOStatement::closeCursor() 要么是一个可选驱动的特有方法（效率最高）来实现，要么是在没有驱动特定的功能时作为一般的PDO 备用来实现。一般的备用语义上与下面的 PHP 代码相同：
<?php
do {
while ($stmt->fetch())
;
if (!$stmt->nextRowset())
break;
} while (true);
?>
成功时返回 TRUE， 或者在失败时返回 FALSE。
Example #1 一个 PDOStatement::closeCursor() 的例子
在下面例子中，$stmt PDOStatement 对象返回多行，但应用程序只取第一行，让 PDOStatement 对象处于一个有未取行的状态。为确保应用程序对所有数据库驱动都能正常运行，在执行 $otherStmt PDOStatement 对象前，$stmt 调用一次 PDOStatement::closeCursor() 。
<?php
/* 创建一个 PDOStatement 对象 */
$stmt = $dbh->prepare('SELECT foo FROM bar');
/* 创建第二个 PDOStatement 对象 */
$otherStmt = $dbh->prepare('SELECT foobaz FROM foobar');
/* 执行第一条语句 */
$stmt->execute();
/* 从结果集中只取出第一行 */
$stmt->fetch();
/* The following call to closeCursor() may be required by some drivers */
$stmt->closeCursor();
/* 现在可以执行第二条语句了 */
$otherStmt->execute();
?>
jhill9693 at gmail dot com (2011-05-02 20:34:45)
If you ran a SQL statement (vs a query that returns data) such as UPDATE, try unsetting your PDOStatement object instead of calling PDOStatement::closeCursor().
narada dot sage at googlemail dot com (2006-04-29 13:23:08)
When running multiple queries one after another especially when stored procedures are involved one must release all result sets and fetch all rows in each result set for a stored procedure before moving onto the next query. This is important because a stored procedure returns an extra (empty) result set as a result of having called the procedure itself.
In my case calling PDOStatement :: closeCursor() did not work (on php-5.1.3-rc2) and I was presented with the following error message: "SQLSTATE[HY000]: General error: 2013 Lost connection to MySQL server during query" upon trying to PDO :: prepare() my second query. So I used the following drop in replacement within one of my classes which fixed the issue.
<?php
/**
* @param PDOStatement $oStm
*/
public static function closeCursor($oStm) {
do $oStm->fetchAll();
while ($oStm->nextRowSet());
}
?>