Parallel Browser Crawler concept

Browser.php

<?php

// Library Code
class Browser
{
    public function createPage(): Page
    {
        return new Page();
    }
}

BrowserTab.php

<?php

class BrowserTab
{
    private Page $page;

    private $isBusy = false;

    public function __construct(Page $page)
    {
        $this->page = $page;
    }

    public function visit(string $url, Closure $closure)
    {
        $this->isBusy = true;
        /* await */ $this->page->visit($url);
        $closure($this->page->getResponse());
        $this->isBusy = false;
    }

    public function isBusy(): bool
    {
        return $this->isBusy;
    }
}

BrowserTabCollection.php

<?php

class BrowserTabCollection
{
    /** @var BrowserTab[] */
    private $browserTabs;

    public function __construct(Browser $browser, int $tabsCount)
    {
        for ($i = 0; $i < $tabsCount; $i++) {
            $this->browserTabs[$i] = new BrowserTab($browser->createPage());
        }
    }

    public function getIdleBrowserTab(): BrowserTab
    {
        while (true) {
            foreach ($this->browserTabs as $browserTab) {
                if (!$browserTab->isBusy()) {
                    return $browserTab;
                }
            }
            usleep(100000);
        }
    }

    public function isBusy(): bool
    {
        foreach ($this->browserTabs as $browserTab) {
            if ($browserTab->isBusy()) {
                return true;
            }
        }
        return false;
    }
}

Crawler.php

<?php

class Crawler
{
    private $queue;

    private $browserTabCollection;

    private $resultStorage = [];

    public function __construct()
    {
        $this->queue = new SplQueue();
        $this->browserTabCollection = new BrowserTabCollection(new Browser(), 5);
    }

    public function crawl(string $url): void
    {
        $this->queue->enqueue($url);

        $this->work();
    }

    private function work()
    {
        $closure = $this->getPageIndexerClosure();

        while (!$this->queue->isEmpty() || $this->browserTabCollection->isBusy()) {
            $url = $this->queue->dequeue();

            $tab = $this->browserTabCollection->getIdleBrowserTab();
            $tab->visit($url, $closure);
        }
    }

    private function getPageIndexerClosure(): Closure
    {
        return function (Response $response) {
            foreach ($this->getAllLinks($response->html) as $url) {
                $this->queue->enqueue($url);
            }
            $this->resultStorage[$response->url] = $response->cookies;
        };
    }

    private function getAllLinks(string $html): array
    {
        // TODO: implement logic
        return [];
    }
}

Page.php

<?php

// Library Code
class Page
{
    public function visit(string $url): void
    {
    }
}

Response.php

<?php

// Library Code
class Response
{
    public $url = '';

    public $html = '';

    public $cookies = [];
}