Incorrect Download link for Subsites


A custom content form for my custom newsletter post type wasn’t saving post content, thus my solution was to ignore the post content and generate it on the fly by getting the attached files instead. This worked beautifully in the main site, unfortunately, on the chinese subsite, wp_get_attachment_url returned something different.

Cause of Problem

It turns out that the _wp_attached_file meta value in the postmeta table is storing the full path to the link in the subsite. The corresponding value for posts in the main site only have the year/month/filename. They don’t contain the full domain name too. What this meant is that for the subsite, wp_get_attachment_url will add the domain to the front of the full link, thus generating an invalid link.


An email to the wp-hackers list had no responses, I’m not sure if it’s because nobody knows anything about it or whether the email got lost. Thus my solution is to filter the function output to strip out the extra baseurl which prepends the domain name. If this is necessary, the post meta is also updated so the next time this is needed, the correct output will be returned and there will no need to strip out the extra domain name again.

add_filter( 'wp_get_attachment_url', 'mbpc_wp_get_attachment_url_filter', 10, 2);

function mbpc_wp_get_attachment_url_filter($url, $postID) {
	$upload_dir = wp_upload_dir();

	//search through the url and see if it contains a 2nd instance of the baseurl
	$pos = strpos( $url, $upload_dir['baseurl'] , 1);

	if ( $pos !== false) {		//2nd instance exists
		$url = substr ($url, $pos);
		//update post meta so it won't have to find the substring on subsequent calls
		update_post_meta( $postID, '_wp_attached_file', substr( $url, strlen( $upload_dir['baseurl'] ) + 1 ));
	return $url;

Newsletters for Subsite

Previously, newsletters on the subsite were put up with default Posts because I hadn’t done the necessary work for the subsite as well. However, to allow for a uniform admin interface, it makes more sense for the chinese newsletters to go up as ‘newsletter’ custom post types as well. Using phpmyadmin and SQL, I changed all the Posts in the subsite to newsletters.

Content Manager Rights

The whole idea is to let a layperson upload the weekly newsletters. This function already exists for the main site. However, to make it work for the subsite, I had to setup the Members plugin and roles all over again. Since everything is stored in the wp_options table, I just had to copy and paste the wp_user_roles option to wp_x_user_roles on the subsite, and copy and paste the members_settings option wp_options to the corresponding options table for the subsite. This has the effect of activating and configuring the members plugin with all the role types I had previously setup on the main site correctly configured on the subsite.


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