Category Archives: PHP

Add custom CSS style to Advanced Custom Fields WYSIWYG field

Example of adding styles from a theme. The code below works on frontend (if you are using acf_form()) as well as in the backend.

add_filter( 'tiny_mce_before_init', function($mce_init) {
  $content_css = get_stylesheet_directory_uri() . '/your-custom-css.css';

  if (isset($mce_init[ 'content_css' ])) {
    $mce_init[ 'content_css' ] = "{$mce_init['content_css']},{$content_css}";

  return $mce_init;


Building the right administration interface for every user

WordPress Stockholm meetup group, January 2017

When building websites a lot of work is put into the frontend of the site – with good reason! But often the experience for content editors and site administrators isn’t given as much thought. However WordPress has a wide array of tools to easily make great admin interfaces.

In this talk we’ll take a look at the ecosystem of administration tools available for WordPress, as well as the different types of users that are likely to use the backend of the sites you build.


Migrating a WordPress Site From HTTP to HTTPS with WP-CLI

It’s as easy as:

Take a backup

wp db export

Test rewriting from HTTP to HTTPS

wp search-replace '' '' --dry-run

If everything is looking good, it’s time to rewrite:

wp search-replace '' ''

Some tutorials recommend adding the --skip-columns=guid flag. The train of thought is that old posts will be visible to RSS readers as new ones. I don’t think this is a big problem, and it’s much cleaner to not keep non-SSL urls in your database. It can also cause issues if you are using the GUID field to grab image urls/ids from attachments. (It’s a very popular way of mapping a URL to an attachment ID). With that in mind, I find it’s best to omit this flag.

Disable GitHub API in Composer to improve speed

If you are using GitHub repositories in Composer, you might notice that it takes a long time to run composer update. This is because Composer uses the GitHub API in an effort to improve performance. Unfortunately, GitHub API is very slow and you might need hundreds of calls for a single repo, depending on the number of tags. You can disable this behaviour by specifying the undocumented no-api flag in Composer. In composer.json, add it like this:

    "type": "vcs", 
    "url": "", 
    "no-api" : true 

This will make Composer check out the repository via Git instead, usually improving composer update times by 2-3x.

Discussion on Reddit with more info on the technical details

More information regarding the no-api flag

See the required PHP version for all your Composer dependencies

After building a project using Composer, you might ask yourself what the lowest supported PHP version amongst all the included libraries is. The highest number would also be the the minimum version PHP version that the project would run on.

To quickly check this in composer, run this from the project root:

composer show -i -t | grep -o "\-\-\(ext-\|php\).\+" | sort | uniq | cut -d- -f3-

Your output might look something like this:

php >=5.3.0
php >=5.3.9
php ^5.5 || ^7.0
php >=5.5.9

By checking the list of versions, we can see that 5.5.9 would be the lowest PHP version we would need to run this project.

Snippet source

Installing WordPress on a tiny wireless router

I recently got a Gl.Inet 6416 router off AliExpress for about $25. It’s an interesting little box that includes many features that routers ten times more expensive lack. (Thanks OpenWRT and open source!) The box is powered by the Atheros AR9331, an aging MIPS architecture processor clocked at a measly 400mhz with 64MB of RAM and 16MB of storage. In computer years, MIPS is stone-age technology, first launched in 1981(!), and the MIPS 24K standard this particular processor implements was first launched in 2004.


But the router is still quite capable even by 2016 standards! There is an SSH server and a package manager, opkg, which has packages for PHP 5.6. I immediately thought of something crazy to do – namely to install WordPress on this poor little machine.

So let’s see how that works.

Scaling things down

64MB of memory can’t accomodate either Apache or MySQL, so we have to find a way to run without them. Luckily, PHP has a built-in web server since version 5.4 that we can use, and WordPress has a SQLite plugin. This is a truly cool plugin that hooks into the db.php drop-ins and dynamically rewrites all WordPress database calls from MySQL to SQLite-compatible syntax.


Increasing the storage

16 MB of internal storage won’t get us far. Luckily, you can insert a USB drive and it happily mounts it under /mnt/sda1, so let’s do that:

IMG_20160717_031209-01 - Copy

Installing dependencies

Let’s SSH into the router and install SQLite, PHP and some useful tools like wget…

opkg install zoneinfo-core sqlite3-cli sqlite3 wget htop ca-certificates php5-cli php5 php5-mod-session php5-mod-pdo-mysql php5-mod-gd php5-mod-hash php5-mod-mbstring php5-mod-json php5-mod-opcache php5-mod-sqlite3 php5-mod-pdo-sqlite

Installing WordPress

Unfortunately, there is no support for Phar archives and hence no simple way to run WP-CLI or Composer, so let’s install WP manually:

cd /mnt/sda1
mv sqlite-integration wordpress/wp-content/plugins

Now let’s move the db.php drop-in into place:

cp wordpress/wp-content/plugins/sqlite-integration/db.php wordpress/wp-content/db.php

Let’s also create a default wp-config.php file:

cp wordpress/wp-config-sample.php wordpress/wp-config.php

Tweaking the PHP config

Some PHP defaults aren’t a good fit for this ancient architecture. Let’s decrease opcache.memory_consumption from 64MB to 8MB and increase the max_execution_time from 30 to 300 in /etc/php.ini

Booting it up

Now let’s finally start this baby up on the built-in PHP web server:

cd wordpress
php-cli -S

Loading up the browser the router IP on port 8080 gives us a familiar sight:

Thanks to the SQLite adapter, we don’t need to provide database credential, an on-disk database has already been created for us in wordpress/wp-content/database/.ht.sqlite.

After about 40 seconds, the install finally finishes!

2016-07-17 02_52_28-Program Manager

So what’s the speed like?

It comes as no surprise that this is suh-low! A pageload takes 5-15 seconds. Sometimes even longer if you are saving a draft or publishing a post:

2016-07-17 02_56_33-Program Manager

Other than that, it does actually run! Although uploading large images tends to make the built-in server crash with an out-of-memory error. Not surprising, considering we only have about 40 MB of RAM to play with (The operating system takes up approximately 25MB RAM).


Even though this is a silly project it shows that it is not only possible to run WordPress on OpenWRT, but that it is fairly pain-free to set up. There are more powerful MIPS processors out there (like the Qulcomm QCA9531 with 650mhz/128MB RAM) and those might actually make this usable for a real site. Hope you learned about some techniques to use WordPress in low-memory environments!

Disable preview in the WordPress theme Customizer

The WordPress Customizer preview can be notoriously buggy. Here is a snippet for easily disabling the customizer preview:

add_action( 'customize_preview_init', function() {
    die("The customizer is disabled. Please save and preview your site on the frontend.");
}, 1);

After adding this code to your themes functions.php file or a plugin, the live preview will simply show a message that it is disabled.

Screen Shot 2016-05-06 at 15.34.11