The pjax middleware Jeffery Way explained on his Pjax Laracasts lesson

FilterIfPjax.php

<?php

namespace App\Http\Middleware;

use Closure;
use Illuminate\Http\Request;
use Illuminate\Http\Response;
use Symfony\Component\DomCrawler\Crawler;

class FilterIfPjax
{
    /**
     * Handle an incoming request.
     *
     * @param  \Illuminate\Http\Request  $request
     * @param  \Closure  $next
     * @return mixed
     */
    public function handle($request, Closure $next)
    {
        $response = $next($request);

        // redirect will fire the middleware again when it comes around, so no need to filter it.
        if(!$request->pjax()  || $response->isRedirection())
        {
            return $response;
        }

        $this->filterResponse($response, $request->header('X-PJAX-CONTAINER'))
             ->setUriHeader($response, $request);

        return $response;
    }

    /**
     * Filters the response by swapping its content with the requested container.
     *
     * @param Response $response
     * @param $container
     * @return $this
     */
    protected function filterResponse(Response $response, $container)
    {
        $crawler = new Crawler($response->getContent());

        // Combines the title tag with the new content, pjax should identify the new tag title
        // and swap it with current (old) title value in the document.

        $response->setContent(
            $this->makeTitle($crawler) .
            $this->fetchContainer($crawler, $container)
        );

        return $this;
    }

    /**
     * Creates the page title and returns it in a title tag.
     *
     * @param Crawler $crawler
     * @return string
     */
    protected function makeTitle(Crawler $crawler)
    {
        $pageTitle = $crawler->filter('head > title')->html();

        return "<title>{$pageTitle}</title>";
    }


    /**
     * Filters and gets the content from the original container.
     *
     * @param Crawler $crawler
     * @param $container
     * @return mixed
     */
    protected function fetchContainer(Crawler $crawler, $container)
    {
        $content = $crawler->filter($container);

        if(! $content->count())
        {
            // No content was found.
            abort(422);
        }

        return $content->html();
    }


    /**
     * Updates the URL in the address bar with the new page url.
     *
     * @param $response
     * @param $request
     */
    protected function setUriHeader(Response $response, Request $request)
    {
        $response->header('X-PJAX-URL', $request->getRequestUri());
    }
}