WordPress上的prettyPhoto特色图片

I am pretty new at this and tried to search a lot about this, breaking my site down numerous times because of wrong PHP code, so here is the deal.

I have a Wordpress page with portfolio posts. In those posts the only image displayed is the featured image. Due to that my prettyPhoto plugin won't show the lightbox when I click on that featured photo.

First I had this code ...

<?php
if ( has_post_thumbnail() ) {
the_post_thumbnail();
}
?>

... which showed the featured image but didn't show the lightbox so it was not clickable. Then I played around and created this:

<?php if ( has_post_thumbnail()) : ?>
<a class="lightbox_single_portfolio" title="<?php echo esc_attr($title); ?>" 
href="<?php echo esc_url($image_src); ?>" data-
rel="prettyPhoto[single_pretty_photo]">
<?php the_post_thumbnail(); ?>
</a>
<?php endif; ?>

So the featured image got clickable, the lightbox started opening but there is an error that states "Image cannot be loaded. Make sure the path is correct and image exists". Due to that I said to myself that the problem could be that lightbox isn't loading the right image source.

I tried playing a bit more and tried to do this ...

<?php 
if ( has_post_thumbnail()) {
$featured_img_url = get_the_post_thumbnail_url(get_the_ID(),'full');
echo '<a class="lightbox_single_portfolio" href="'.esc_url($image_src).'" data-rel="prettyPhoto[single_pretty_photo]">'; 
the_post_thumbnail('thumbnail');
echo '</a>';
endif;?>

... aaaand it breaks my site. What could be the problem?

You are not closing the If statement,

change endif; to }

Well, I'm gonna post an answer as I found out something on the internet and it made my code work. Although the above answer (change endif; to }) did make my code work, it still showed the same error that the path couldn't be found.

I played around again a little bit, and this did the trick:

 <?php 
 if ( has_post_thumbnail()) {
   $large_image_url = wp_get_attachment_image_src( get_post_thumbnail_id(), 'full');
   echo '<a rel="prettyPhoto" href="' . $large_image_url[0] . '" title="' . the_title_attribute('echo=0') . '" >';
   the_post_thumbnail();
   echo '</a>';
 }
 ?> 

So the PHP calls a $large_image_url instead of the post thumbnail url. This did the trick, and it works! It shows my featured image in a lightbox :)