Combine portfolio filter with lightbox gallery

Hi,

How can I combine the portfolio filter with the lightbox gallery?
I use this code, but the filter isn't working:

<div id="portfolio" class="portfolio grid-container portfolio-2 portfolio-masonry clearfix" data-big="3" data-lightbox="gallery">

  <article class="portfolio-item pf-photo pf-fineer">
    <div class="portfolio-image">
      <a href="images/realisaties/photo1.jpg" data-lightbox="gallery-item">
        <img src="images/realisaties/photo1.jpg" alt="Gallery Image">
        <div class="overlay"><div class="overlay-wrap"><i class="icon-line-plus"></i></div></div>
      </a>
    </div>
  </article>
  <article class="portfolio-item pf-photo pf-fineer">
    <div class="portfolio-image">
      <a href="images/realisaties/photo2.jpg" data-lightbox="gallery-item">
        <img src="images/realisaties/photo2.jpg" alt="Gallery Image">
        <div class="overlay"><div class="overlay-wrap"><i class="icon-line-plus"></i></div></div>
      </a>
    </div>
  </article>
  <article class="portfolio-item pf-photo pf-fineer">
    <div class="portfolio-image">
      <a href="images/realisaties/photo3.jpg" data-lightbox="gallery-item">
        <img src="images/realisaties/photo3.jpg" alt="Gallery Image">
        <div class="overlay"><div class="overlay-wrap"><i class="icon-line-plus"></i></div></div>
      </a>
    </div>
  </article>

</div><!-- #portfolio end -->

Thanks in advance.

JW