How does WP detect format type (and can I make use of this)?

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When I make a post with a theme that supports (all) post formats, WordPress will suggest the format type it thinks best fits my post.

How does it do this? Is it possible to leverage this in, say, my own WP plugin?

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Update: As far as I know, this is built-in functionality. As shown in the image.

1 Answer
1

This functionality appears to be exclusively a feature of the block editor. It’s not especially clever either. All it does is check that if the post has 1 or 2 blocks (and no more), and then maps the first block against a list of appropriate post formats, like so:

switch ( name ) {
    case 'core/image':
        return 'image';
    case 'core/quote':
    case 'core/pullquote':
        return 'quote';
    case 'core/gallery':
        return 'gallery';
    case 'core/video':
    case 'core-embed/youtube':
    case 'core-embed/vimeo':
        return 'video';
    case 'core/audio':
    case 'core-embed/spotify':
    case 'core-embed/soundcloud':
        return 'audio';
}

This is part of the getSuggestedPostFormat() selector function that’s part of the core/editor data store. You can see the full source in the Gutenberg repository here. This seems like a good overview of what the data stores in the block editor are.

To use this function in JS in the editor you could use:

wp.data.select('core/editor').getSuggestedPostFormat();

The logic is simple enough that it’s trivial to implement in PHP with parse_blocks(), but since it’s based on the blocks used it would only be useful for content built with the block editor.

function wpse_346884_get_suggested_post_format( $content ) {
    if ( ! has_blocks( $content ) ) {
        return null;
    }

    $block  = null;
    $blocks = parse_blocks( $post->post_content );

    if ( 1 === count( $blocks ) ) {
        $block = $blocks[0]['blockName'];
    }

    if ( 2 === count( $blocks ) ) {
        if ( 'core/paragraph' === $blocks[1]['blockName'] ) {
            $block = $blocks[0]['blockName'];
        } 
    }

    switch ( $block ) {
        case 'core/image':
            return 'image';
        case 'core/quote':
        case 'core/pullquote':
            return 'quote';
        case 'core/gallery':
            return 'gallery';
        case 'core/video':
        case 'core-embed/youtube':
        case 'core-embed/vimeo':
            return 'video';
        case 'core/audio':
        case 'core-embed/spotify':
        case 'core-embed/soundcloud':
            return 'audio';
    }

    return null;
}

Then you might want to implement some additional logic to make sure the theme supports the returned post type.

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