wp_get_attachment_link filter not working

Question

I'm trying to modify all image attachment links to include a rel value thus:

add_filter( 'wp_get_attachment_link', 'my_prettyadd', 100, 6);

function my_prettyadd( $markup, $id, $size, $permalink, $icon, $text ) {
    $content = preg_replace("/<a/","<a rel=\"prettyPhoto[slides]\"",$markup,1);
    return $content;
}

This has worked fine for me for ages, but recent installation of WP have meant this fails in so far that the function is never called (I placed an exit; line in there and it has no effect. I know that my theme does not use wp_get_attachment_link and so I'm suspecting I'm barking up the wrong tree now.

I'm using Canvas by WooThemes - I don't know if they have done anything out of the ordinary with attachments in posts. Anything obviously wrong in what I"m doing?

Answer 1

Have you tried using the 'the_content' filter? Something like this should probably do the Job , note that i have not had the time to test this .

function my_prettyadd($content) {
    global $post;
    $pattern        = "/(<a(?![^>]*?rel=['\"]prettyPhoto.*)[^>]*?href=['\"][^'\"]+?\.(?:bmp|gif|jpg|jpeg|png)['\"][^\>]*)>/i";
    $replacement    = '$1 rel="prettyPhoto['.$post->ID.']">';
    $content = preg_replace($pattern, $replacement, $content);
    return $content;
 }
 add_filter("the_content","my_prettyadd");

simple regex that will add a rel to all images on the website