<?php

if (!class_exists('PP_Attachment')) {
    class PP_Attachment
    {
        public function __construct()
        {
            add_filter('attachment_fields_to_edit', array($this, 'custom_attachment_field_link'), 10, 2);
            add_filter('attachment_fields_to_save', array($this, 'custom_attachment_field_link_save'), 10, 2);
        }
        public function custom_attachment_field_link($form_fields, $post)
        {
            $form_fields['pp-custom-link'] = array('label' => __('PP - Custom Link', 'powerpack'), 'input' => 'text', 'value' => get_post_meta($post->ID, 'pp-custom-link', true));
            return $form_fields;
        }
        public function custom_attachment_field_link_save($post, $attachment)
        {
            if (isset($attachment['pp-custom-link'])) {
                update_post_meta($post['ID'], 'pp-custom-link', $attachment['pp-custom-link']);
            }
            return $post;
        }
    }
    new PP_Attachment();
}