How to get the_post_thumbnail caption?

Question

I want to show the caption of the post thumbnail, there's a couple of methods out there, but none of them displays the caption properly, the caption just float and not displayed under the image! I want to wrap the image in wp-caption div, like any other images with caption.

Here is the function I've tried

function monahans_thumbnail_caption($html, $post_id, $post_thumbnail_id, $size, $attr)
{
  $attachment =& get_post($post_thumbnail_id);

  // post_title => image title
  // post_excerpt => image caption
  // post_content => image description

  if ($attachment->post_excerpt || $attachment->post_content) {
    $html .= '';
    if ($attachment->post_excerpt) {
      $html .= ''.$attachment->post_excerpt.' ';
    }
    $html .= $attachment->post_content.'
';
  }

  return $html;
}

add_action('post_thumbnail_html', 'monahans_thumbnail_caption', null, 5);

As I said, the caption doesn't show properly at all:



I want a function to wrap the image inside wp-caption div, and wrap the caption text inside wp-caption-text

Answer 1

Use the shortcode handler img_caption_shortcode to render the HTML for you, though you do need to pass it a width (which we can easily get with wp_get_attachement_image_src:

function wpse_138126_thumbnail_caption( $html, $post_id, $post_thumbnail_id, $size, $attr ) {
    if ( $post = get_post( $post_thumbnail_id ) ) {
        if ( $size = wp_get_attachment_image_src( $post->ID, $size ) )
            $width = $size[1];
        else
            $width = 0;

        $html = img_caption_shortcode(
            array(
                'caption' => trim( "$post->post_excerpt $post->post_content" ),
                'align'   => 'alignright',
                'width'   => $width,
            ),
            $html       
        );
    }

    return $html;
}

add_filter( 'post_thumbnail_html', 'wpse_138126_thumbnail_caption', 10, 5 );