Introducing: Linkify for Chrome

In WordPress 4.2, a fun little feature was quietly snuck into Core, I’m always delighted to see people’s reactions when they discover it.

But there’s still a problem – WordPress is only ~26% of the internet, how can you get the same feature on the other 74%? Well, that problem has now been rectified. Introducing, Linkify for Chrome:

Thank you to Davide for creating Linkify’s excellent icon!

Linkify is a Chrome extension to automatically turn a pasted URL into a link, just like you’re used to in WordPress. It also supports Trac and Markdown-style links, so you can paste links on your favourite bug trackers, too.

Speaking of bug trackers, if there are any other link formats you’d like to see, post a ticket over on the Linkify GitHub repo!

Oh, and speaking of Chrome extensions, you might be like me, and find the word “emojis” to be extraordinarily awkward. If so, I have another little extension, just for you.

How I Would Solve Plugin Dependencies

lol, I wouldn’t1.


1. If I absolutely had to, I wouldn’t do it the same as Ryan.

WordPress isn’t (and will never be) Linux

ZYpp is the dependency solver used by OpenSUSE (and its PHP port in Composer), it was born of the need to solve complex dependency trees. The good news is, WordPress doesn’t have the same problem, and we shouldn’t create that problem for ourselves.

One of the most common-yet-complex issues is determining how to handle different version requirements by different packages. If My Amazing Plugin requires WP-API 1.9, but Your Wonderful Plugin requires WP-API 2.0, we have a problem. There are two ways to solve it – Windows solves it by installing multiple versions of the dependency, and loading the correct version for each package. This isn’t a particularly viable option in PHP, because trying to load two different versions of the same code in the same process is not my idea of a fun time.

The second option, which ZYpp solves, is to try and find a mutually compatible version of the dependency that each plugin can use. The biggest problem with this method is that it can’t always find a solution. If there’s no compatible way of installing the libraries, it has to throw back to the user to make the decision. This isn’t a viable option, as 99.999*% worth of users wouldn’t be able to tell the difference between WP-API versions 1.9 and 2.0, and nor should they.

But there’s a third option.

Technical Debt as a Service

Code libraries are, by their nature, developer facing. A user never really needs to know that they exist, in the same way that they don’t need to know about WP_Query. In WordPress Core, we strive for (and often achieve) 100% backwards compatibility between major versions. If we were going to implement plugin dependencies, I would make it a requirement that the code libraries shoulder the same burden: don’t make a user choose between upgrades, just always keep the code backwards compatible. If you need to make architectural changes, include a backwards compatible shim to keep things working nicely.

This intentionally moves the burden of upgrading to the developer, rather than the end user.

What Version?

If we’re going to require library developers to maintain backwards compatibility, we can do away with version requirements (and thus, removing the need for a dependency solver). If a plugin needs a library, it can just specify the library slug.

Better Living Through Auto Updates

If we were to implement plugin dependencies, I think it’d be a great place to introduce auto updates being enable by default. There’s no existing architecture for us to take into account, so we can have this use the current WordPress best practices. On top of that, it’s a step towards enabling auto updates for all Core releases, and it encourages developers to create backwards compatible libraries, because their library will almost certainly be updated before a plugin using it is.

Let’s Wrap This Up

I’m still not convinced plugin dependencies is a good thing to put in Core – it introduces significant complexities to plugin updates, as well as adding another dependency on WordPress.org to Core. But it’s definitely a conversation worth having.

JSON Encoding in WordPress 4.1

Earlier in the year, we noticed a problem with JSON in WordPress. The JSON spec very explicitly notes that it only supports UTF-8, whereas WordPress can use any character set that MySQL supports. So, for sites that didn’t use MySQL’s utf8 or utf8mb4 character sets, this generally presented itself as json_encode() returning false; which resulted in either invalid JSON being returned from an Ajax request, or a JavaScript error in some embedded code.

To fix this, WordPress 4.1 now includes a shiny new function that we recommend for all plugins and themes:

wp_json_encode()

Usage for wp_json_encode() is identical to json_encode(). It works by trying a json_encode(), then checking if that encoded properly. If it failed, wp_json_encode() will go through whatever lump of data you passed to it, convert it to UTF-8, then return it as JSON.

Have fun with WordPress 4.1, and see you next year for new and exciting functionality coming to a WordPress install near you!

The Next Adventure

Over my past few years at Automattic, I’ve worked on a bunch of different teams and projects – VideoPress, the WordPress iOS app, various Social projects, and most recently, o2. I even took a few months to work on WordPress core, helping build the auto-update functionality that we now see rolling out security updates within hours of their release.

The few months I spent working on WordPress core made me realise something – there’s a lot more I have to contribute. So, with the WordPress 4.0 RC out the door, I’m super excited to be moving to my next project – working on WordPress core full time!

Automattic naturally puts a lot of people-hours into WordPress, with over 30 of us contributing to WordPress 3.9. I’m looking forward to being a bigger part of that, and giving more back to WordPress community!

WordPress and UTF-8

Update: WordPress 4.2 has full UTF-8 support! There’s no need to upgrade manually any more. ?

For many years, MySQL had only supported a small part of UTF-8, a section commonly referred to as plane 0, the “Basic Multilingual Plane”, or the BMP. The UTF-8 spec is divided into “planes“, and plane 0 contains the most commonly used characters. For a long time, this was reasonably sufficient for MySQL’s purposes, and WordPress made do with this limitation.

It has always been possible to store all UTF-8 characters in the latin1 character set, though latin1 has shortcomings. While it recognises the connection between upper and lower case characters in Latin alphabets (such as English, French and German), it doesn’t recognise the same connection for other alphabets. For example, it doesn’t know that ‘Ω’ and ‘ω’ are the upper and lower-case versions of the Greek letter omega. This creates problems for searching text, when you generally want to match characters regardless of their case.

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With the release of MySQL 5.5, however, the utf8mb4 character set was added, and a whole new world opened up. Plane 1 contains many practical characters from historic scripts, music notation and mathematical symbols. It also contains fun characters, such an Emoji and various game symbols. Plane 2 is dedicated to CJK Ideographs, an attempt to create a common library of Chinese, Japanese and Korean characters.

For many websites, being able to use Emoji without installing an extra plugin is an excellent reason to switch your WordPress database to utf8mb4, but unfortunately it’s not quite that simple. MySQL still has a few more limitations that cause problems with  utf8mb4.

Without further ado, here’s how to configure MySQL, so that WordPress can use utf8mb4. If you don’t have the ability to configure your MySQL server directly, you should speak to your host. If they don’t want to, it’s probably time to look for a new host.

Upgrade MySQL

You need to be running MySQL 5.5.14, or higher. If you’re not already running at least MySQL 5.5 (ideally 5.6), you should be doing that anyway, as they provides significant performance and stability improvements over previous versions. For help with upgrading MySQL, check out the MySQL manual.

Configure MySQL

Before we convert your tables, we need to configure MySQL correctly.

In your my.cnf file, add the following settings to the [mysqld] section. Remember to double check that you’re not duplicating settings in your my.cnf file – if any of these options are already set to something different, you’ll need to change that setting, rather than add a new setting.

You’ll need to restart your MySQL server after adding these settings.

Use InnoDB

Next, convert your WordPress tables to InnoDB and utf8mb4:

You’ll need to run these two queries for each WordPress table, I used wp_posts as an example. This is a bit tedious, but the good news is that you’ll only ever need to run them once. A word of warning, you should be prepared for some downtime if you have particularly large tables.

Configure WordPress

Finally, you can tell WordPress to use utf8mb4 by changing your DB_CHARSET setting in your wp-config.php file.

And there you have it. I know, it’s not pretty. I’d really like to add this to WordPress core so you don’t need to go through the hassle, but currently only a very small percentage of WordPress sites are using MySQL 5.5+ and InnoDB – in order to justify it, we need to see lots of sites upgrading! You can head on over to the core ticket for further reading, too – login and click the star at the top to show your support, there’s no need to post “+1” comments. 🙂

Oh, and a final note on Emoji – Chrome support is pretty broken. There’s an extension to add Emoji to Chrome, but it interferes with WordPress’ post editor. If you really want to use Emoji in your posts, Safari or Firefox would be better options.

Don’t Let Your Plugin Be Activated on Incompatible Sites

When you write a WordPress plugin, you can specify a minimum WordPress version that your code is compatible with, using the “Requires” option in your plugin header, but it isn’t enforced. Along with that, there’s no way to specify a minimum version of PHP or MySQL.

This can cause your users to have bad experiences with your plugin, and you’ll get bad ratings.

So, here’s how I make sure my plugins are only activated when I want them to be.

 

It’s only a little extra code when added to a plugin, provides complete protection, and won’t cause any weirdness on the front end of your site, it’ll just deactivate itself either on activation, or when someone visits wp-admin.

Don’t Do Regular Expressions, Use The DOM

I’m as guilty of this as anyone – I have a lump of HTML that I need to extract information from. So, I write a quick regular expression, knowing full well that they’re not appropriate for the job. But I do it anyway.

This time, I decided to try doing things a better way.

Here’s the problem I’m trying to solve. In o2, (here’s a feature preview for you!) we’re experimenting with the idea of having post tags inline with the post content, instead of as a separate text field, like in P2. So, when a user saves a post with “#foo” in it, this needs to be extracted and saved as a tag “foo”.

With a regular expression, extraction seems pretty easy at first:

That works on a simple text string, but things start to get complicated pretty quickly. What happens when you enter a URL, like http://pento.net/#foo? Or even worse, enter the URL in a tag like <a href="http://pento.net/#foo">...</a>? In both of these cases, “#foo” clearly isn’t meant to be a tag, so your regular expression quickly becomes a mess. Eventually, it gets to the point where you can’t even guarantee it’ll work under all cases.

Enter DOM parsing.

We’re all pretty familiar with dealing with the DOM, thanks to JavaScript, but it remains a less popular choice on the server side. PHP has various built in libraries to help, and there are plenty of wrappers for the PHP libs, as well as independent implementations, some of which are listed here. There are pros and cons to each option, so far nothing has appeared with the ubiquity of jQuery.

For this exercise, we’ll use PHP’s native DOM extension.

To begin with, let’s create a function to extract the tags from a new post, and save them.

 

So far, this is all pretty straight forward. Our find_tags() function is where all the magic happens.

The easiest way to explain how this works is to walk through it, so let’s do that now. We’ll feed find_tags() some basic HTML:

Line 5: We load our HTML into the DOM. The <?xml encoding="UTF-8"> is to force DOMDocument to treat our HTML as being encoded as UTF-8 – by default it assumes ISO-8859-1 (latin1).

Line 7-8: DOMDocument supports XPath selectors, which saves us so much hassle. If you’re not familiar with XPath, it’s kind of like jQuery selectors, but for XML. So, with the //text() selector, we grab an array of all the text nodes in the HTML, “#foo “, “#baz” and ” text”. This fixes one of our big problems, detecting if something is inside of a HTML tag – the DOM library does all of the heavy lifting for us.

Line 10: Now we need to check each text node, to see if it contains a tag.

Line 11-17: But before we do that, we need to make sure we’re not inside a tag we don’t care about. In this example, we assume that anything inside a <pre>, <code> or <a> tag isn’t a post tag, so we can safely ignore it. This loop walks up through the text node’s parents, to make sure it’s not inside one of these tags. This eliminates the “#baz” text node, which is inside an <a> tag.

Line 19-22: Finally, we check the text node for tags, finding the “#foo” tag.


The code is significantly longer than a regular expression, but it has a couple of clear advantages:

  • The function operates exactly as you expect, it only finds tags where you want it to.
  • The regular expression to find tags remains simple, it doesn’t have to care about the hundreds of edge cases you might encounter.

So there you have it. DOM parsing in PHP isn’t a land of monsters, it’s actually pretty easy to wrap your head around, and write code that does exactly what you want it to do.

For an amusing postscript: While writing this post, I ran into a problem with a HTML minification plugin removing the blank lines in the code blocks, because it was just blindly removing all blank lines. By using a DOM parser, instead, it would’ve been able to remove blank lines from everywhere except inside <pre> or <code> tags.

UPDATE (2013-12-19): Fixed a few bugs in the sample code. Props mdawaffe.

How To Backup Before Automatic Updates

When I originally wrote Automatic Updater, I had an action trigger just before the update, so site owners could easily take a backup snapshot, in case of a catastrophic failure. Now that we have Automatic Updates in WordPress Core, however, there’s no such action, and with good reason.

Backups Are Slow

We’re not talking 10-20 seconds slow. We’re talking minutes, or even hours, if the backup includes everything you’ve every uploaded. Some hosts kill processes that take too long, so WordPress might never get to update. Alternatively, it’s possible the backup could still be running when WordPress tries to run the update again, which could potentially cause conflicts.

So with this in mind, how should you do backups before an automatic update runs?

Backup Incrementally

If your backup software doesn’t know how to make an incremental backup, you need to get rid of it, and buy better backup software. I’m naturally biased towards VaultPress, which my employer makes, but there are plenty of good options available. Incremental backups are faster, so it’s easier for you to take backups on a more regular basis – even multiple times a day!

Schedule Your Backups

Instead of running your backup exactly when the update runs, you can schedule a cron job to run 5 minutes before (adjust as needed for the time your backups take). It’s a little tricky to determine if an update is going to run, so here’s a gist you’re welcome to use for your own purposes.

Have fun, stay safe, and remember to test your backups!