Frederick Ding 12:57 am on July 9, 2013
Tags: migration-portability ( 9 ), weekly-update ( 35 )

Migration update: WP Relocate

This past week, I’ve focused primarily on bringing a usable interface to the WP_Relocate class that I posted about last week. While the WP_Relocate class file itself was meant to be something that could be bundled into another suite and reused, the fruits of this week’s labour come in the form of an installable pluginPlugin A plugin is a piece of software containing a group of functions that can be added to a WordPress website. They can extend functionality or add new features to your WordPress websites. WordPress plugins are written in the PHP programming language and integrate seamlessly with WordPress. These can be free in the WordPress.org Plugin Directory https://wordpress.org/plugins/ or can be cost-based plugin from a third-party.

In actuality, the plugin hooksHooks In WordPress theme and development, hooks are functions that can be applied to an action or a Filter in WordPress. Actions are functions performed when a certain event occurs in WordPress. Filters allow you to modify certain functions. Arguments used to hook both filters and actions look the same. are very shallow — merely used to add a menu link (for now). The most important part is the practically-standalone interface.

The design intent was to make this look and feel just like the installer — or the upgrade.php script for database schema changes.

This has been tested against 3.5.2 and 3.6 only. Despite differences in how these versions handle revisions, the changes made to post content are still revertible in either version:

I can test this in code to my heart’s content (except for the difficulties using the current unit-tests framework against older versions of coreCore Core is the set of software required to run WordPress. The Core Development Team builds WordPress.) but nothing beats running it on live site data, especially sites that have posts and uploads from earlier versions of WordPress. As you might imagine, live data is more difficult to generate and test against. I don’t yet know how well this process works with hundreds or thousands of posts, in terms of the time it takes and the level of verbosity communicated to the site administrator.

If you’re interested in trying this out (please don’t use it on a production siteProduction Site A production site is a live site online meant to be viewed by your visitors, as opposed to a site that is staged for development or testing. — it’s probably not ready for that), feel free to:

download it: relocate-1.0.1.zip (GPG sig); or
check it out from SVN.

It installs into wp-content/plugins. The included readme.html file contains more detailed instructions. If anyone tries it out, I’d love to hear if it broke your site. 🙂

What’s next? This week, I am forking the importer plugin that works with WXR files, to examine and fix its issues with fetching attachments from the source. I hope to add some ability to replace URLs using the WP_Relocate class to smooth out the process of copying content from another installation.

Edit (2013-07-09): updated to 1.0.1 with fix for PHPPHP The web scripting language in which WordPress is primarily architected. WordPress requires PHP 5.6.20 or higher versions before 5.4.0.

#migration-portability, #weekly-update

Brad Touesnard 1:25 am on July 9, 2013

Hi Frederick, I’m curious, have you taken a look at https://wordpress.org/plugins/wp-migrate-db/? Or the pro version for that matter? I haven’t dug into your code yet, but it sounds like you’re doing some great work here. Keep it up!
- Frederick Ding 1:31 am on July 9, 2013
  
  Hi Brad, I had come across the site for WP Migrate DB pro version while researching, but hadn’t seen the free edition. It looks like your pluginPlugin A plugin is a piece of software containing a group of functions that can be added to a WordPress website. They can extend functionality or add new features to your WordPress websites. WordPress plugins are written in the PHP programming language and integrate seamlessly with WordPress. These can be free in the WordPress.org Plugin Directory https://wordpress.org/plugins/ or can be cost-based plugin from a third-party is very useful for producing a database dump for export!
  
  I think I have a slightly different use case in mind. The utility of this plugin is that it’s “in-place”. But in reality, all of this is merely a preface to later improvements that I’ve planned for the WXR-based importer/exporter. The plugin UIUI User interface helps me to do all of the testing that unit testing won’t cover!
  
  Thank you for your encouragement!
Ryan McCue 1:31 am on July 9, 2013

This looks fantastic! I’m a big fan of the decision to use revisionsRevisions The WordPress revisions system stores a record of each saved draft or published update. The revision system allows you to see what changes were made in each revision by dragging a slider (or using the Next/Previous buttons). The display indicates what has changed in each revision.; have you given thought to creating an undo functionality? (This would probably mean also storing copies of option data, which could be expensive.)
- Frederick Ding 1:34 am on July 9, 2013
  
  Thanks! Indeed, I’ve thought about a rollback ability (after all, things can go wrong when it’s iterating over all the posts and options).
  
  It might not be as expensive as one might imagine: one would only need to store copies of options that have changed, and we could probably clear all transients when running the process in either direction. (Darn, I wish I had thought of skipping transients earlier.)
  - Ryan McCue 2:46 am on July 9, 2013
    
    It might not be as expensive as you might imagine: one would only need to store copies of options that have changed, and we could probably clear all transients when running the process in either direction. (Darn, I wish I had thought of skipping transients earlier.)
    
    I hadn’t thought about that either; great idea!
JakePT 5:36 am on July 9, 2013

This looks great! But can I use it to move a site from, say http://website.com/old to http://website.com/new?

I just tried something similar and got this error:
“Error: The old site URLURL A specific web address of a website or web page on the Internet, such as a website’s URL www.wordpress.org provided cannot be used in the replacement process”

Should also note the accompanying PHPPHP The web scripting language in which WordPress is primarily architected. WordPress requires PHP 5.6.20 or higher error:
Warning: preg_match_all() expects at least 3 parameters, 2 given in /home/demomagi/public_html/package/wp-content/plugins/relocate/class-wp-relocate.php on line 299
- Frederick Ding 6:20 am on July 9, 2013
  
  Hey Jake,
  
  Thanks for your feedback. My bad! I was following PHP documentation for preg_match_all not realizing that the 3rd parameter didn’t become optional until 5.4.0, hence the error in older versions of PHPPHP The web scripting language in which WordPress is primarily architected. WordPress requires PHP 5.6.20 or higher. And yes, WordPress needs to work with PHP as old as 5.2.4 (that was from 2007!). I’ll make this correction and update the download immediately.
  
  But to answer your first question, yes, you absolutely can use it for that replacement. It was just the PHP preg_match_all compatibility issue that threw off the URLURL A specific web address of a website or web page on the Internet, such as a website’s URL www.wordpress.org validation.
  - JakePT 6:40 am on July 9, 2013
    
    Thanks for the quick fix! I’ll give it a try.
Shea Bunge 5:36 am on July 9, 2013

A word of warning: be careful when getting the user to directly access a .php file from the wp-content directory – lots of users blockBlock Block is the abstract term used to describe units of markup that, composed together, form the content or layout of a webpage using the WordPress editor. The idea combines concepts of what in the past may have achieved with shortcodes, custom HTML, and embed discovery into a single consistent API and user experience. direct access to these files. It might be better to hook to template_redirect and check for a custom query var, and load your interface there instead.
- Frederick Ding 6:12 am on July 9, 2013
  
  You’re right about the issues with that — disabling direct access to .php files in wp-content is a sensible security approach (although plugins and themes do sometimes use direct access — such as in the case of timthumb and CSSCSS Cascading Style Sheets. minifying plugins).
  
  The issue with hooking into something like template_redirect is that I’m not sure it would load early enough. The script somewhat needs to operate independently of WordPress because it can’t rely on the “old” site URLURL A specific web address of a website or web page on the Internet, such as a website’s URL www.wordpress.org to work — just as upgrade.php and install.php do — and the other possible alternative is to ask that users drop this file elsewhere (as Ryan suggests when using the JSON API as part of core).
mattyrob 1:01 pm on July 11, 2013

Hi Frederick. This looks like a very worthwhile project to me. I’ve just repaired a whole bunch of corrupt serialized data for attachments in the postmeta table for two of my site that probably came from a previous version of WordPress (I can’t think it was a pluginPlugin A plugin is a piece of software containing a group of functions that can be added to a WordPress website. They can extend functionality or add new features to your WordPress websites. WordPress plugins are written in the PHP programming language and integrate seamlessly with WordPress. These can be free in the WordPress.org Plugin Directory https://wordpress.org/plugins/ or can be cost-based plugin from a third-party as I’ve never used a media plugin).

Anyway, I needed to use wp_update_attachment_metadata() and wp_generate_attachment_metadata() to apply the fixes quickly and effectively.

I’m replying as I note in 1.0.1 of your code you are using wp_insert_attachment() to update some of hte postmeta but the codex for that function indicates that the above 2 functions should be called as well. I thought you might want to look at that for rebuilding the attachment postmeta while you fix up the other table entries.

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Migration update: WP Relocate

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