Convert pw_gallery to file_list

pw_convert_pw_gallery_to_file_list.php

<?php
/*
Plugin Name: Convert pw_gallery to file_list
Plugin URI: https://github.com/mustardBees/cmb-field-gallery
Description: Rough, inefficient snippet for converting existing data from pw_gallery to file_list format. Hit example.com/?convert_pw_gallery_to_file_list. Use at your own risk. Backup first!
Version: 1.0.0
Author: Phil Wylie
Author URI: https://www.philwylie.co.uk/
License: GPL2
*/

function pw_convert_pw_gallery_to_file_list() {
	if ( ! isset( $_GET['convert_pw_gallery_to_file_list'] ) ) {
		return;
	}

	$boxes = CMB2_Boxes::get_all();

	$gallery_fields = array();

	foreach ( $boxes as $box ) {
		foreach ( $box->meta_box['fields'] as $key => $field ) {
			if ( 'pw_gallery' === $field['type'] ) {
				$gallery_fields[] = $key;
			}
		}
	}

	$gallery_fields = array_unique( $gallery_fields );

	foreach ( $gallery_fields as $gallery_field ) {
		global $wpdb;

		$meta_ids = $wpdb->get_col( $wpdb->prepare(
			"
			SELECT meta_id FROM $wpdb->postmeta
			WHERE meta_key = '%s'
			",
			$gallery_field
		) );

		foreach ( $meta_ids as $meta_id ) {
			$old = get_metadata_by_mid( 'post', $meta_id );
			$values = $old->meta_value;

			reset($values);
			$first_key = key($values);

			if ( 0 === $first_key ) {
				$new = array();

				foreach( $values as $value ) {
					$new[$value] = wp_get_attachment_url( $value );
				}

				update_metadata_by_mid( 'post', $meta_id, $new );
			}
		}
	}
}
add_action( 'cmb2_after_init', 'pw_convert_pw_gallery_to_file_list' );