Description:
------------
If I take code from http://php.net/manual/en/mysqli.poll.php and add 2 var_dump's/print_r's (see my code), that code starts to generate "Commands out of sync; you can't run this command now"

So as I understand we can't use var_dump() for the connection at this stage. It would be great to describe it in the documentation.

Test script:
---------------
<?php
$link1 = mysqli_init();
mysqli_real_connect($link1, 'dbm1.d4','developer','developerovich');
mysqli_query($link1, "SELECT version() as ver", MYSQLI_ASYNC);

$all_links = array($link1);
$processed = 0;
do {
    $links = $errors = $reject = array();
    foreach ($all_links as $link) {
        $links[] = $errors[] = $reject[] = $link;
    }

var_dump($links); // !!! this var_dump cause the problem
    if (!mysqli_poll($links, $errors, $reject, 1)) {
        continue;
    }
print_r($links); // it shows us that we have text in the$mysqli->error object
    foreach ($links as $link) {
        if ($result = $link->reap_async_query()) {
            print_r($result->fetch_assoc());
            if (is_object($result))
                mysqli_free_result($result);
        } else die(sprintf("MySQLi Error: %s", mysqli_error($link)));
        $processed++;
    }
} while ($processed < count($all_links));


Expected result:
----------------
So, as I understand, we can't call var_dump()/ print_r between:
mysqli_query(...., MYSQLI_ASYNC) and mysqli_poll(...)
It would be great to cover this nuance  in the documentation. Or as a better option, fix var_dump/print_r() to work correctly with mysqli connections with async requests.

Actual result:
--------------
last print_r shows this:

Array
(
    [0] => mysqli Object
        (
            [affected_rows] => -1
            [client_info] => mysqlnd 5.0.11-dev - 20120503 - $Id: 7f4b7f0657d4ab15d8fdac13f23f696de5283a89 $
            [client_version] => 50011
            [connect_errno] => 0
            [connect_error] => 
            [errno] => 2014
            [error] => Commands out of sync; you can't run this command now
            [error_list] => Array
                (
                    [0] => Array
                        (
                            [errno] => 2014
                            [sqlstate] => HY000
                            [error] => Commands out of sync; you can't run this command now
                        )

                )

            [field_count] => 0
            [host_info] => XXXXX via TCP/IP
            [info] => 
            [insert_id] => 0
            [server_info] => 5.5.28-log
            [server_version] => 50528
            [stat] => 
            [sqlstate] => HY000
            [protocol_version] => 10
            [thread_id] => 268564296
            [warning_count] => 0
        )

)