17.php

<?php

use Symfony\Component\DomCrawler\Crawler;

require __DIR__ . '/vendor/autoload.php';

#####################################################

function parallel_map(callable $func, array $items) {
    $childPids = [];
    $result = [];
    foreach ($items as $i => $item) {
        $newPid = pcntl_fork();
        if ($newPid == -1) {
            die('Can\'t fork process');
        } elseif ($newPid) {
            $childPids[] = $newPid;
            if ($i == count($items) - 1) {
                foreach ($childPids as $childPid) {
                    pcntl_waitpid($childPid, $status);
                    $sharedId = shmop_open($childPid, 'a', 0, 0);
                    $shareData = shmop_read($sharedId, 0, shmop_size($sharedId));
                    $result[] = unserialize($shareData);
                    shmop_delete($sharedId);
                    shmop_close($sharedId);
                }
            }
        } else {
            $myPid = getmypid();
            echo 'Start ' . $myPid . PHP_EOL;
            $funcResult = $func($item);
            $shareData = serialize($funcResult);
            $sharedId = shmop_open($myPid, 'c', 0644, strlen($shareData));
            shmop_write($sharedId, $shareData, 0);
            echo 'Done ' . $myPid . ' ' . formatUsage(memory_get_peak_usage()) . PHP_EOL;
            exit(0);
        }
    }
    return $result;
}

function first($array) {
    return reset($array);
}

function reduce(callable $func, array $array, $initial = null) {
    return array_reduce($array, $func, $initial);
}

function clearUrl($url) {
    return preg_replace('#\&sid=.{32}#s', '', $url);
}

function formatUsage($memory) {
    return number_format($memory / 1024 / 1024, 2, '.', ' ') . ' Mb';
}

#####################################################

function normalizeUrl($url) {
    return 'http://yiiframework.ru/forum/'. ltrim($url, './');
}

function getHtml($url) {
    $file = __DIR__ . '/cache/' . md5($url);
    if (file_exists($file)) {
        return file_get_contents($file);
    } else {
        $html = file_get_contents($url);
        file_put_contents($file, $html);
        return $html;
    }
}

function crawler($url) {
    return new Crawler(getHtml(normalizeUrl($url)));
}

function getForumMaxPageNumber($forumUrl) {
    return max(
        first(crawler($forumUrl)
            ->filter('div.action-bar.bar-top .pagination li:nth-last-of-type(2)')
            ->each(function (Crawler $link) {
                return intval($link->text());
            })),
        1
    );
}

function getForumPages($forumUrl) {
    echo 'Forum pages for ' . clearUrl($forumUrl) . PHP_EOL;
    return array_map(function ($number) use ($forumUrl) {
        return $forumUrl . ($number > 1 ? '&start=' . (25 * ($number - 1)) : '');
    }, range(1, getForumMaxPageNumber($forumUrl)));
}

function getForumPageTopics($forumPageUrl) {
    echo 'Forum page topics for ' . clearUrl($forumPageUrl) . PHP_EOL;
    return crawler($forumPageUrl)
        ->filter('ul.topiclist.topics li dl')
        ->each(function (Crawler $topic) {
            $link = $topic->filter('div.list-inner a.topictitle');
            return [
                'title' => $link->html(),
                'url' => $link->attr('href'),
                'count' => intval($topic->filter('dd.posts')->text()) + 1,
            ];
        });
}

$forumUrl = './viewforum.php?f=28';

$topics =
    reduce('array_merge',
        parallel_map('getForumPageTopics',
            getForumPages($forumUrl)), []);

echo 'Done ' . formatUsage(memory_get_peak_usage()) . PHP_EOL;

echo clearUrl(print_r($topics[0], true));

echo PHP_EOL;