Wordpress: How should I keep an xml-file updated with the images attached to a page?

If I want to keep an xml file updated with all the images that a us开发者_C百科er has attched to a page, I shouldn't write create and generate an xml-file everytime someone visits that page (because it would cause too much overhead) - should I create and fill the file when the user attaches new content to the page in the admin console instead?

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First, you will need to create directory under wp-content. Lets called it wp-content/xmlimages/ Now, copy this code and paste it to wp-content/plugins/cr-attachmentpost2xml.php:

<?php
/*
Plugin Name: CR Attachment Post To XML
Plugin URI: http://bayu.freelancer.web.id/search/plugin
Description: Automatically create XML files for each post that list post attachment of that particular post.
Version: 0.1
Author: Arief Bayu Purwanto
Author URI: http://bayu.freelancer.web.id/

*/

add_action('publish_post', 'cr_attachmentpost2xml_publish_post_hook');

//add_action('admin_menu', 'cr_attachmentpost2xml_test');

function cr_attachmentpost2xml_publish_post_hook( $post_id ){
    __cr_attachmentpost2xml_impl( $post_id );
    return $post_id;
}

function cr_attachmentpost2xml_test(){
    __cr_attachmentpost2xml_impl( 738 );
}

function __cr_attachmentpost2xml_impl( $post_id ){
    $udir = wp_upload_dir();
    $writepath = $udir['basedir'] . '/xmlimages/';
    $attachment = get_children( 'post_type=attachment&post_parent=' . $post_id);

    if(wp_is_post_revision($postId)) return $post_id;
    //print_r($attachment);
    $xml = "<?xml version=\"1.0\"?>";
    $xml .= "<attachments>";

    foreach($attachment as $att){
        $image_src = wp_get_attachment_image_src( $att->ID );
        $xml .= "<attachment>";
        $xml .= "<id>{$att->ID}</id>";
        $xml .= "<date>{$att->post_date}</date>";
        $xml .= "<title>{$att->post_title}</title>";
        $xml .= "<mime_type>{$att->post_mime_type}</mime_type>";
        $xml .= "<url>".$image_src[0]."</url>";

        $xml .= "</attachment>";
    }
    $xml .= "</attachments>";
    file_put_contents($writepath . $post_id . ".xml", $xml);
    //echo "$xml";
}

WARNING: Don't except something special here, as it's just a quick & dirty code. Hope it work the way to want and if you do use this code, don't forget to check for any security hole it might introduce.

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Any particular reason why you need this? This data is recorded by WordPress so why not instead create a simple API that returns XML on request? There's no sense in duplicating data.