Description:
------------
 SQL statement that return or should return a statement could leave an open cursor that cannot be closed.


This bug is related to the following previous reports

https://bugs.php.net/bug.php?id=36347
https://bugs.php.net/bug.php?id=34499
https://bugs.php.net/bug.php?id=42499

It's been reported that sql statement that do return result could cause this issue in non trivial situations.
This report also highlight that statement returning empty result set could also cause the issue.

Test script:
---------------
$dbh = new PDO("mysql:your connection string", '', '');

echo $dbh->exec("SELECT * FROM cube where false");
echo $dbh->exec("SELECT * FROM cube where false");
print_r($dbh->errorInfo());

Expected result:
----------------
00

Actual result:
--------------
0Array
(
    [0] => HY000
    [1] => 2014
    [2] => Cannot execute queries while other unbuffered queries are active.  Consider using PDOStatement::fetchAll().  
Alternatively, if your code is only ever going to run against mysql, you may enable query buffering by setting the PDO::
MYSQL_ATTR_USE_BUFFERED_QUERY attribute.
)