Although using the Lightbox plugin can be a nice way of giving your readers a great experience in viewing your images in your blog, it can also become a bit tedious adding the rel=”lightbox” attribute to each image that you want to open with it. But thanks to Tyler Longren‘s code snippet, you won’t have to anymore.

Copy/paste the code below in to your functions.php file. Once done, every image you embed in a post will automatically have a rel=”lighbox” attribute added to it.

add_filter('the_content', 'my_addlightboxrel');

function my_addlightboxrel($content) {

global $post;

$pattern ="/<a(.*?)href=('|\")(.*?).(bmp|gif|jpeg|jpg|png)('|\")(.*?)>/i";

$replacement = '<a$1href=$2$3.$4$5 rel="lightbox" title="'.$post->post_title.'"$6>';

$content = preg_replace($pattern, $replacement, $content);

return $content;
 }

And by the way, in line 5 of the code you can change the rel=”lightbox” to whatever you prefer as Tyler noted that some viewer scripts use rel=”thumbnail” among other things. This snippet also adds the post title as the title attribute of the image’s anchor tag.

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