Description:
------------
execute two sequence query cause error when they only in two different class.

the following code run WELL.
<?php
$db_host    = 'localhost';
$db_name    = 'jeon';
$db_port    = '3506';
$db_user    = 'test';
$db_pwd     = 'test';

$db = new PDO("mysql:host=$db_host;dbname=$db_name;port=$db_port", $db_user, $db_pwd, array(PDO::ATTR_PERSISTENT => true));
$db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

$r = $GLOBALS['db']->prepare("SELECT COUNT(*) FROM teacher WHERE teacherid=? AND password=?");
$r->execute(array('a', 'a'));

$r = $GLOBALS['db']->prepare("SELECT COUNT(*) FROM teacher WHERE teacherid=? AND password=?");
$r->execute(array('b', 'b'));
?>

But if i move the query code to different class, it does not working and raise a error.
"General error: 2014 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."

only when i insert $r->closeCursor(); in the first class, they are working.

sorry for my bad english. ;)

Reproduce code:
---------------
<?php
$db_host    = 'localhost';$db_name    = 'jeon';$db_port    = '3506';$db_user    = 'test';$db_pwd     = 'test';
$db = new PDO("mysql:host=$db_host;dbname=$db_name;port=$db_port", $db_user, $db_pwd, array(PDO::ATTR_PERSISTENT => true));
$db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
class Session{
    public function start_new() {
        $r = $GLOBALS['db']->prepare("SELECT COUNT(*) FROM teacher WHERE teacherid=? AND password=?");
        $r->execute(array('b', 'b'));
    }
}
class Test{
    function dotest() {
        $r = $GLOBALS['db']->prepare("SELECT COUNT(*) FROM teacher WHERE teacherid=? AND password=?");
        $r->execute(array('a', 'a'));
        //$r->closeCursor();
        $GLOBALS['session']->start_new();
    }
}
$session = new Session();$test = new Test();$test->dotest();
?>