ACF: Custom Field for Media Item

The img_caption_shortcode example from the WordPress codex is a good skeleton structure to jump off of to add custom fields and adjust the markup to suit your needs.

Example of output with caption and photo credit underneath photo

In the following example, my ACF field is called “photo_credit” and is connected to any image file in the media gallery.

This will allow you to display additional information automatically (similar to a caption).

Targeting a media item

Something to keep in mind when getting custom fields that are attached to something like a media file is that you’ll need to pass a second parameter to target the media it is connected to.

One way of getting this corresponding ID is to use preg_match & regex to split the number off before the $attr are defined in the example below.

 * Customize <img> shortcode markup..
add_filter( 'img_caption_shortcode', 'my_img_caption_shortcode', 10, 3 );
function my_img_caption_shortcode( $empty, $attr, $content ){

	preg_match( '/(\d+)$/', $attr['id'], $matches );
	$media_id = $matches[1];
	$credit = get_field( 'photo_credit', $media_id );

	$attr = shortcode_atts( array(
		'id'      => '',
		'align'   => 'alignnone',
		'width'   => '',
		'credit'  => $credit,
		'caption' => '',
	), $attr );

	if ( 1 > (int) $attr['width'] || empty( $attr['caption'] ) ) {
		return '';

	if ( $attr['id'] ) {
		$attr['id'] = 'id="' . esc_attr( $attr['id'] ) . '" ';

     return '<div ' . $attr['id']
     . 'class="wp-caption ' . esc_attr( $attr['align'] ) . '" style="max-width: ' . ( 10 + (int) $attr['width'] ) . 'px;">'
     . do_shortcode( $content )
     . '<p class="wp-caption-text">' . $attr['caption'] . '</p><p class="photo-credit">' . $attr['credit'] . '</p></div>';
Additional Reading:

2 thoughts on “ACF: Custom Field for Media Item

  1. This is exactly what I needed.

    I’m shocked that there isn’t a well-developed plugin to handle an image credit use-case. But this code was easy enough and worked exactly as expect.

    Now to style it with css!

  2. Exactly what I searched for. Thank you. Unfortunately it seems img_caption_shortcode (as well as image_send_to_editor) does not work with Gutenberg anymore. Do you know a way to get this working with Gutenberg? Cheers, Alf

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