WordPress：add_filter for wp_get_attachment_link ADD target param

Question

So I'm trying to figure out how to modify the wp_get_attachment_link function with a filter. I'd like to be able to add the target='_blank' attribute to the anchor.

This is what I've tried but it isn't working:

function modify_attachment_link( $markup, $id, $size, $permalink, $icon, $text )
{
    // We need just thumbnails.
    if ( 'thumbnail' !== $size )
    {   // Return the original string untouched.
        return $markup;
    }

    // We have stored the new URL in a post meta field.
    // See http://wordpress.stackexchange.com/q/3097 for an example.
    $new_url = get_post_meta( $id, 'extra_url', TRUE );

    if ( empty ( $new_url ) )
    {   // There is no URL.
        return $markup;
    }

    // Recreate the missing information.
    $_post      = & get_post( $id );
    $post_title = esc_attr( $_post->post_title );

    if ( $text ) 
    {
        $link_text = esc_attr( $text );
    } 
    elseif ( 
           ( is_int( $size )    && $size != 0 ) 
        or ( is_string( $size ) && $size != 'none' ) 
        or $size != FALSE 
    ) 
    {
        $link_text = wp_get_attachment_image( $id, $size, $icon );
    } 
    else 
    {
        $link_text = '';
    }

    if ( trim( $link_text ) == '' )
    {
        $link_text = $_post->post_title;
    }

    return "<a href='$new_url' title='$post_title' target='_blank'>$link_text</a>";
}

add_filter( 'wp_get_attachment_link', 'modify_attachment_link', 10, 6 );

Perhaps some of what's going on here isn't even useful, but I really need the target attribute.

Answer 1

Something like this should work assuming there isn't already a "target" attribute in the link. If there is then this would insert a second one.

<?php
function modify_attachment_link($markup) {
    return preg_replace('/^<a([^>]+)>(.*)$/', '<a\\1 target="_blank">\\2', $markup);
}
add_filter( 'wp_get_attachment_link', 'modify_attachment_link', 10, 6 );
?>