Default Featured Image

常见问题

我选择的特色图片没有显示，为什么不起作用？

This plugin works out of the box for most cases, but not always. If it doesn’t work you can try the following things.

• Switch themes. Most of the time the theme does something weird.
• Are you using the Core WordPress functions to get the image? (see the FAQ below this one).
• Do normal feature images work?
• Might it be hidden via css? DFI images have an extra default-featured-img class added to them.

Still having problems? I want to know if it fails, so contact me

我可以使用哪些功能来显示特色图像？

There are no new functions, all core WordPress functions can be used.

• the_post_thumbnail / get_the_post_thumbnail Display the image.
• the_post_thumbnail_url / get_the_post_thumbnail_url Get the url.
• has_post_thumbnail If a DFI is set it will always return true.
• get_post_thumbnail_id will return the ID set on the post or the DFI.

Can I set a different image for a custom post type?

Yes, the following code will set a different image.

add_filter( 'dfi_thumbnail_id', 'dfi_posttype_book', 10, 2 );
function dfi_posttype_book( $dfi_id, $post_id ) {
    $post = get_post( $post_id );
    if ( 'book' === $post->post_type ) {
        return 31; // the image id for the book post type.
    }

    return $dfi_id; // the original featured image id.
}

Can I set different images per category?

Yes, the following snippet will set different images based on the category.

add_filter( 'dfi_thumbnail_id', 'dfi_category', 10, 2 );
function dfi_category( $dfi_id, $post_id ) {
    // Set a different image for posts that have the 'cats' category set.
    // This will trigger first, if multiple categories have been set.
    if ( has_category( 'cats', $post_id ) ) {
        return 7; // cats img id.
    }
    // Set a different image for posts that have the 'cats' category set.
    if ( has_category( 'dogs', $post_id ) ) {
        return 8; // dogs img id.
    }

    return $dfi_id; // the original featured image id.
}

Can I change the HTML of the default featured image?

When a Default Featured Image is used it will already add an extra class default-featured-img.
This can be used for styling.

If you need more you can change the whole HTML with the filter dfi_thumbnail_html.

add_filter( 'dfi_thumbnail_html', 'dfi_add_class', 10, 5 );
function dfi_add_class( $html, $post_id, $default_thumbnail_id, $size, $attr ) {
    // Add a class to the existing class list.
    $attr['class'] .= ' my-class';

    return wp_get_attachment_image( $default_thumbnail_id, $size, false, $attr );
}

Can I exclude one page from having a Default Featured Image?

The following code will exclude the post/page with ID 23.

add_filter( 'dfi_thumbnail_id', 'dfi_skip_page', 10, 2 );
function dfi_skip_page( $dfi_id, $post_id ) {
    if ( $post_id == 23 ) {
        return 0; // invalid id.
    }

    return $dfi_id; // the original featured image id.
}