(PHP 5 >= 5.3.0)
mysqli::poll -- mysqli_poll — Poll connections
Object oriented style
&$read
   , array &$error
   , array &$reject
   , int $sec
   [, int $usec
  ] )Procedural style
&$read
   , array &$error
   , array &$reject
   , int $sec
   [, int $usec
  ] )This function is currently not documented; only its argument list is available.
Poll connections. Available only with mysqlnd. The method can be used as static.
read
error
reject
secNumber of seconds to wait, must be non-negative.
usecNumber of microseconds to wait, must be non-negative.
   Returns number of ready connections in success, FALSE otherwise.
  
Example #1 A mysqli_poll() example
<?php
$link1 = mysqli_connect();
$link1->query("SELECT 'test'", MYSQLI_ASYNC);
$all_links = array($link1);
$processed = 0;
do {
    $links = $errors = $reject = array();
    foreach ($all_links as $link) {
        $links[] = $errors[] = $reject[] = $link;
    }
    if (!mysqli_poll($links, $errors, $reject, 1)) {
        continue;
    }
    foreach ($links as $link) {
        if ($result = $link->reap_async_query()) {
            print_r($result->fetch_row());
            mysqli_free_result($result);
            $processed++;
        }
    }
} while ($processed < count($all_links));
?>
The above example will output:
Array
(
    [0] => test
)