lakegull

function display_exif_fields ( $form_fields, $post ){

$type = get_post_mime_type( $post->ID );

$attachment_path = get_attached_file( $post->ID );

$metadata = wp_read_image_metadata_exif( $attachment_path );

$city = get_post_meta( $post->ID, 'city', true );
$locationname = get_post_meta( $post->ID, 'locationname', true );

  $form_fields['city'] = array(
    'label' => 'City',
    'input' => 'text',
    'value' => !empty($city) ? $city : $metadata['city'],
    'helps' => '',
  );
  
  $form_fields['locationname'] = array(
    'label' => 'Location name',
    'input' => 'text',
    'value' => !empty($locationname) ? $locationname : $metadata['locationname'],
    'helps' => '',
  );

    return $form_fields;
}

add_filter( 'attachment_fields_to_edit', 'display_exif_fields', 10, 2 );


function save_exif_fields( $post, $attachment ) {

		$array = [ 'city', 'locationname' ];
		foreach ( $array as $one ) {
			if ( ! empty( $attachment[ $one ] ) ) {
				update_post_meta( $post[ 'ID' ], $one, $attachment[ $one ] );
			} else {
				delete_post_meta( $post[ 'ID' ], $one );
			}
		}

		return $post;
	}

	add_filter( 'attachment_fields_to_save', 'save_exif_fields', 10, 2 );

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2. копируете область таба и без опции регекспа меняете на ничего
   
3. \n, меняете на ,
   
4. ,\n меняете на , дважды