Description:
------------
I'm just switching to mysqlnd to be able to use http://php.net/manual/en/book.mysqlnd-ms.php but I see some serious performance degradation compared to libmysql. That degradation is not documented and PHP documentation states that mysqlnd is dropped in replacement when in fact.

NewRewlic for my application shows more 100ms spend in PHP after switching to mysqlnd https://db.tt/68r9RfhJ

I've created a benchmark to reproduce to problem, it's quite simple (ignore the fact I'm creating prepared statement in every iteration; it's just for testing only):

Orders table contains 91 columns.

$dbh = new PDO("mysql:host=$host; dbname=$dbname;", $user, $pass);

for ($i = 0; $i < 1000; $i++) {
    $sth = $dbh->prepare("SELECT * FROM Orders LIMIT 100");
    $sth->execute();

    $result = $sth->fetchAll(PDO::FETCH_ASSOC);
}

Execution time:
libmysql - 2 seconds
mysqlnd - 3 seconds (50% more)