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I am pulling data from an external web service into a custom post type. This data includes images. How can I create an image gallery, add some existing attachments to it, and associate it with a post?

What I was hoping to find is something like a set_post_gallery counterpart to the get_post_gallery function, but I can't find anything like it in the codex, on google, or in wp-includes/media.php.

This is how I set up the attachments:

$attachment = [
  'guid' => wp_upload_dir()[ 'url' ] . '/' . basename( $path ),
  'post_mime_type' => wp_check_filetype( basename( $path ), null )[ 'type' ],
  'post_title' => "$mlsNum $id",
  'post_content' => '',
  'post_status' => 'inherit'
];

$attachmentId = wp_insert_attachment( $attachment, $path, $this->postId );

// Generate attachment metadata and create resized images.
wp_update_attachment_metadata( $attachmentId, wp_generate_attachment_metadata( $attachmentId, $path ));

And this is how I am trying to retrieve the gallery for the theme:

$gallery = get_post_gallery( $post, false );
var_dump( $gallery );
var_dump( $post );

$post is defined, and $gallery is false. I was under the impression that wp_insert_attachment would create a gallery for the post and add the attachment to it, but apparently this is not the case. If it was, then that would cause other problems for me when I go to attach a PDF to the post.

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1  
Just had a look in the get_post_gallery function. It is regexing the post content for the gallery shortcode. That means if no shortcode present, no post gallery will be returned. –  Jörn Lund Mar 27 at 10:11

2 Answers 2

up vote 2 down vote accepted

When you just have raw image files, that you want to assign to a post, wp_insert_attachment will do the job.

With attachments already present in your database you can use wp_update_post to set the attachment's post_parent. Like this:

wp_update_post( array(
    'ID' => $attachment_id,
    'post_parent' => $parent_post_id,
));

To recieve a post's attachments you can use get_children.

$args = array(
    'post_parent' => $parent_post_id,
    'post_type' => 'attachment',
);
$attachments = get_children( $args );

If you insist on using get_post_gallery– that will only return image attachments—you should add the [gallery] shortcode to your parent post content.

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I also though wp_insert_attachment would add the attachment to the post's default gallery, creating it if necessary, but the codex makes no such promise (and the magic doesn't work for me). I wonder how the admin interface creates galleries... –  Dan Ross Mar 24 at 18:49
    
There is no default gallery that I am aware of. A gallery is only identified by the image's IDs in the gallery shortcode. You could use the suggested get_children() to get all the attachments, or alternatively save the attachment IDs as meta for the parent post. –  helgatheviking Mar 27 at 11:17
    
I have been using get_children and checking mime_type as a temporary solution, but I will switch to the [gallery] shorcode method so that the user can edit the gallery using the WP media manager on the post edit page. This will also make the plugin easier to integrate with other people's themes. I am not the first person to work on this site, and I probably won't be the last. It feels a little hackish to mess with the post content to manipulate the gallery, but it will do the job and there is no better way. Thanks Jörn! –  Dan Ross Mar 27 at 16:38

There's a great PHP solution here which will add the gallery editor to the custom post type editor - great, if like me, you are creating custom post types using PHP and importing data using WPAllImport. In this case, I want to ensure I use the default gallery so I can allow my clients to edit/add/delete imported images.

The code below adds the gallery editor to your custom post type editor interface:

https://gist.github.com/alexdunae/897503

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Sigh, it's an iframe hack... but +1, it looks like it would work, and we have nothing better. It's because of stuff like this that I am now strongly favouring frameworks over CMSs. –  Dan Ross Oct 5 at 19:40

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