#32: attachment_fields_to_save

attachment_fields_to_save.php

<?php
/**
 * Save custom attachment meta
 *
 * @see wp_ajax_save_attachment_compat(), media_upload_form_handler(), edit_post()
 *
 * @param array $post The attachment attributes.
 * @param array $attachment_data An array of attachment fields.
 *
 * @return array The attachment attributes.
 */
function wpdocs_custom_attachment_meta( $post, $attachment_data ) {
	// If the field has a value, update post meta
	if ( isset( $attachment_data['image_editor_name'] ) && ! empty( sanitize_text_field( $attachment_data['image_editor_name'] ) ) )
		update_post_meta( $post['ID'], 'image_editor_name', sanitize_text_field( $attachment_data['image_editor_name'] ) );

	return $post;
}
add_filter( 'attachment_fields_to_save', 'wpdocs_custom_attachment_meta', 10, 2 );