How can I reference external attachments without breaking core WordPress files?

Question

How can I reference external attachments without breaking core WordPress files?

Brettins

2021年7月18日 09:00

I am developing a site that uses WooCommerce WordPress to show a fair amount (10,000+) products, and can't accommodate the size of all the images for the products. So, I'm leaving the images on their CDN, and making all the image attachments references to the external URLs.

This required a bit of hacking, as WooCommerce/WordPress will try to take the images and upload them and set the attachment URL to a local relative path (eg, 2018/02/), and then when the images are called later on the site, the wp_get_attachment_url will add the uploads directory to the base image, giving something like site.com/wp-content/uploads/2018/02/whatever.jpg.

Basically what I've done to make this all pan out is

Stop WordPress from running the wp_generate_attachment_metadata by setting it to return true as soon as the function is called, which prevents the image from being downloaded and from being copied into the uploads directory.
Upload the products from a CSV
Run a MySQL query to copy the woocommerce source image URL on to the attachment location
Override wp_get_attachment_url to not append the uploads directory to attachment images

Essentially, a couple of 1 line changes to the WordPress core. Which is bad, because any time in the future when the site updates it'll just bork the changes.

Is there a healthier way to approach this?

Topic woocommerce-offtopic core-modifications hacks csv Wordpress

Category Web

filipecsweb · Accepted Answer · 2019年3月3日 00:28

Pay attention to the comments along the snippet.

<?php
/**
 * Filters the attachment URL.
 *
 * @param   string $url    URL for the given attachment.
 * @param   int    $att_id Attachment post ID.
 *
 * @return  string  $url Custom URL for the given attachment.
 */
function wp_get_attachment_url_callback( $url, $att_id ) {
    // Instead of keeping full path we actually need just 'wp-content/uploads'.
    // And we do this the right way, dynamically, calling functions and constants.
    $uploads_dir         = wp_get_upload_dir()['basedir'];
    $partial_uploads_dir = str_replace( ABSPATH, '', $uploads_dir );

    // Check if attachment file is in WordPress uploads directory.
    if ( strpos( $url, $partial_uploads_dir ) === false ) {
        return $url;
    }

    // Just for reference, until now, the $url is still something like:
    // http://example.com/wp-content/uploads/2019/03/image.jpg

    /**
     * @TODO    Define the right CDN URL here.
     */
    $new_site_url = 'http://cdn-domain.com';
    $pattern      = get_site_url();
    $url          = preg_replace( "#$pattern#", $new_site_url, $url );

    // Again, just for reference, now the $url looks like:
    // http://cdn-domain.com/wp-content/uploads/2019/03/image.jpg

    return $url;
}

add_filter( 'wp_get_attachment_url', 'wp_get_attachment_url_callback', 999, 2 );

I hope it enlightens you so you can achieve your goal.

How can I reference external attachments without breaking core WordPress files?

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