Why X Theme and Pro sometimes cause PHP warnings on WPEngine

The Problem

Earlier this fall I was working on an e-commerce site that’s hosted on WPEngine that used Themeco’s Pro as its parent theme most pages hadn’t seen any customization yet, most of the code was stock, and this appeared on the Products page:

PHP Warning:  Invalid argument supplied for foreach() in wp-content/mu-plugins/wpengine-common/plugin.php

Hmm. Who is passing what to a foreach?

It turns out that both X Theme and it’s progeny Pro do this turn off WordPress’s automatic responsive images:

// Disable WordPress 4.4 Responsive Images
// =============================================================================

if ( ! function_exists( 'x_disable_wp_image_srcset' ) ) :
  function x_disable_wp_image_srcset( $source ) {
    return false;
  add_filter( 'wp_calculate_image_srcset', 'x_disable_wp_image_srcset' );

They’re hooking into the wp_calculate_image_srcset filter and returning false, which stops WordPress from adding a srcset attribute to an image, (more on why in a moment). The problem here is that the value being passed to the filter, $sources, is an array, but x_disable_wp_image_srcset() turns that array into a boolean false, so then anything else hooking into wp_calculate_image_srcset, for example, WPEngine’s CDN system, tries to iterate over the $sources array, but it’s not an array, hence the error. By filtering $sources to a boolean false Themeco is breaking the expected, and documented, behaviour of the wp_calculate_image_srcset filter.


Luckily, there are two easy fixes for this problem. The first is to make sure you’re using the latest version of WPEngine’s must-use plugin. They’ve caught on to the problem and check to make sure $sources is actually an array:

if ( is_array( $sources ) ) {
    foreach ( $sources as $source ) {
        // do the stuff

If you can’t do that, at least Themeco made the function pluggable, so you can add your own version of x_disable_wp_image_srcset() to your theme’s functions.php or a plugin that returns an empty array and plays nicely with other plugins:

// This is a pluggable function. If we don't define it here then Pro does in 
// pro/framework/functions/global/admin/thumbnails/setup.php
function x_disable_wp_image_srcset( $sources, $size_array, $image_src, $image_meta, $attachment_id ) {
    return [];

Or, you could use responsive images.

Confusion, (aka, why this happens in the first place)

When I first discovered this problem I E-mailed Themeco to tell them about the problem, however they pointed me at the documentation for the wp_calculate_image_srcset() function, which states the function can return false, and sent me on my way:

Hey John,

Thanks for writing in. In looking over WordPress' official documentation for that function/hook, I believe that boolean false should be the correct value to return:


In the "Return" section you'll see that it is supposed to return a string or a boolean false if there is an "error or only one source exists." It seems as though WPEngine should need to revise their function to account for these instances anyway even if not for X or Pro (and at least work to catch any fatal errors like this).

Hopefully that helps, cheers.

Best Regards,
Your Themeco Team

This confusion occurs because the convention in WordPress is that if a filter and a function have the same name, the filter filters the output of the function. However, in this case the convention is broken – when I raised the issue in the Advanced WordPress Facebook group a very experienced WP developer made the exact same mistake and assumed that allowable return types for the function should be fine to return from the filter. After we cleared up the confusion I filed a bug about the confusing names, go star it so it gets some attention!

A Fluke of PHP

So why does returning false in the wp_calculate_image_srcset filter stop WordPress from using responsive images? Here’s the relevant code from media.php:

$sources = apply_filters( 'wp_calculate_image_srcset', $sources, $size_array, $image_src, $image_meta, $attachment_id );

// Only return a 'srcset' value if there is more than one source.
if ( ! $src_matched || count( $sources ) < 2 ) {
    return false;

To follow along, if $sources is turned into a boolean false at the apply_filters() call, then a count( false ) happens in the condition on the next non-comment line. Instead of an error like I expected, running count() on any non-array value returns 1, so count( false ) == 1, also count( 0 ) == 1


First, be a good citizen of the WordPress ecosystem and don’t change the type of a filtered value to something other than the documented types for that value. Second, if you have any non-core themes or plugins installed you can’t trust that a value coming into a filter will be the type that the docs say, so check! When WPEngine realized there was a problem an is_array() fixed the problem. Third, read support E-mails thoroughly and make sure you understand them, it hurts when I go to the effort to document a problem and come up with a solution, and I’m told it’s not a problem. Finally, go +1 my ticket so maybe others won’t get bitten.

A PHP Version Switcher for the AMP stack on OS X

A friend is thinking about buying MAMP Pro so he can test on different versions of PHP. Since I just set up version-switching myself, for free, here’s how I did it. Hopefully it’ll save someone a bit of money or frustration.

This is happening on a Mac, with the latest version of OS X, (Currently 10.11.3 El Capitan), using the pre-installed version of Apache, and Homebrew as a package manager.

Step 1: Install more than one version of PHP on your system

Using Homebrew you can install a version of PHP, then “unlink” it so it’s not currently being used:

brew install php7
brew unlink php7

If you want to be able to switch PHP versions on the command-line there’s a tool called PHP Version that does the heavy lifting for you, and with Homebrew it’s easy to install.

Step 2: Make it easy to change the PHP version Apache is using

First, stop the main Apache config, (/etc/apache2/httpd.conf), file from loading PHP. Find any line that mentions PHP modules and comment it out, (put a # at the beginning of the line). For example:

#LoadModule php5_module libexec/apache2/libphp5.so
#LoadModule php5_module /usr/local/opt/php56/libexec/apache2/libphp5.so

Now we need an Apache config file for each PHP version that you want to run. I’ve put these files in /etc/apache2/other/ and used the file extension “.conffile” to prevent Apache from auto-loading them:

A screenshot of /etc/apache2/conf/other

Each of your .conffile files needs to have the location of the PHP library, and any extra PHP info. This is the contents of my php-7.conffile:

LoadModule php7_module /usr/local/opt/php70/libexec/apache2/libphp7.so
<IfModule php7_module>
    AddType application/x-httpd-php .php
    AddType application/x-httpd-php-source .phps
<IfModule dir_module>
    DirectoryIndex index.html index.php

php-5.conffile is very similar, but has the path of the PHP 5 .so file and the IfModule conditional checks for php5_module.

If you have any existing php*.conf files in /etc/apache2/other/ they can be blank.

Next we need to make an easy way to tell Apache to use one of the .conffiles, which I’ve  done by creating a symbolic link to the one I want to use. Since I don’t like typing out ln commands I’ve created a script, which I call php-v.sh.

if [ $1 = 7 ]; then
`sudo ln -Fs /etc/apache2/other/php-$PHP_VERSION.conffile /etc/apache2/other/php.conf`
`sudo apachectl graceful`
echo "PHP version switched to $PHP_VERSION"

This script symlinks /etc/apache2/other/php.conf to the .conffile that I want to use, (using the -F switch to overwrite the old symlink), and restarts Apache. It needs sudo so it’ll ask for your password.

Finally, it’s nice to have php-v.sh available from everywhere, so I’ve created a symlink from ~/bin/php-v, which is in my PATH, to the actual script:

ln -s /Users/John/Developer/Scripts/php-v.sh /Users/John/bin/php-v

And now I can switch PHP versions at will:A screenshot of my terminal, having just switched PHP versions quickly & easily!

Show the OmniFocus Tasks You Did Today on your Desktop

This morning Ken Case retweeted this:

Using Automator, not TextExpander

I’ve wanted a solution to show me what I accomplished in a day for a while, but I don’t use TextExpander. Luckily Colter Reed’s script to log today’s completed OmniFocus tasks is Javascript for Automation, which can be run with the built-in OSX app, Automator, so I built an Automator workflow that runs the script, (I just pasted Colter Reed’s script into an Automator “Run Javascript” action, then made one tweak when I ran into a small problem). If you’ve never used Automator before don’t worry – I hadn’t either! Here’s my Automator workflow file, (it’ll need to be unzipped). It returns a bunch of text, which we’ll deal with next.

Put the Results on your Desktop with GeekTool

GeekTool can take text from a shell script and display it on your desktop, and you can set it to refresh that text however often you want. I created a new shell Geeklet with GeekTool with the following script:

Automator Runner ~/Developer/Scripts/omnifocus-completed.workflow | sed -e 's/^"//' -e 's/"$//' -e 's/\\"/"/g'

For some reason the Automator Runner returns the text with quotation marks around it, so the parts after the pipe remove the quotation marks, (using instructions from Stackoverflow).

When choosing your refresh interval keep in mind that the script grabs focus from OmniFocus when it runs, which will be annoying if you are working in OmniFocus and you have a short refresh interval. I also don’t know how much battery this will eat for those of us on laptops.

With some font & colour tweaking, my desktop now looks like this:


Update (October 9, 2015): This morning a bunch of tasks I did last night, but before midnight, were still on my desktop, so I went debugging. It looks like OmniFocus, (at least my version, which is a pre-release test version), is exposing the completedDate value to Javascript as a UTC date/time, but with a Timezone offset set, so things done in the evening might remain on the list of “today’s” completed tasks, (this might reverse on the other side of the world, with things you do in the morning not appearing). To fix this I’ve modified the startOfDay() function to take the Timezone Offset into account. I assume this is a bug and will be temporary, so I’m not updating the downloadable Automator action above. Here’s the updated startOfDay() function:

function startOfDay() {
// The day started at midnight this morning
    var d = new Date(),
    hours = 0,
    minutes = 0;
    if( d.getTimezoneOffset() !== 0 ) {
        hours = Math.round( d.getTimezoneOffset() / 60 );
        minutes = d.getTimezoneOffset() % 60;
    d.setHours( hours );
    d.setMinutes( minutes );
    d.setSeconds( 0 );
    return d;

Update (November 3, 2015): I used quotation marks in a task name, and they came out escaped on my desktop. I’ve updated the command line for the geeklet to strip the slashes from before double quotation marks;

Vanilla Speed

Me: I wonder how to make this cool new HTML5 feature interact with Javascript properly.


Stack Overflow Answer #1: Use this great jQuery function!

Stack Overflow Answer #2: Underscore.js is better, us it! You only need 1/2 a character of code.

Smacks desk in frustration.

I’m working on a major overhaul of an existing website that focuses on speed and a great mobile experience that has never used Javascript libraries, (it was originally written in 2007 before they were a thing), and we’re not changing that. For this website a library is a bunch of extra code to download, execute, and take up memory, which adds extra function calls between the code I write and the things that happen in the browser – more CPU cycles, more battery drain, more waiting, and no benefit to our users and customers.

If we were using jQuery I wouldn’t have spent some time looking up the differences in event creation between browsers, and I might not have spent the morning figuring out why a datalist wasn’t appearing properly in Firefox, or maybe I would have had to do that bit of debugging anyway. One thing that doesn’t help me move the project along at all is other people’s over-reliance on Javascript libraries that is so prevalent. In 2007 when I had a problem I could Google it, or post to a forum, and find an answer, (assuming it had been done before), today I experience the sequence of events at the top of this post several times every day. This is why the trio of blog posts last week, (Marco Arment’s post about PPK’s post about John Gruber’s take on Facebook Instant), have really resonated with me. PPK is right, we need to stop relying on libraries, whether it’s jQuery, underscore, or whatever. There are times when a library is the right tool, but with modern Javascript APIs, HTML5, and CSS3, and good browser support for all but the absolute bleeding-edge.

To use a Javascript library is to externalize the cost of development onto your customers and users.

Despite my frustration with the “use some library” responses on Stack Overflow questions using plain vanilla JavaScript has turned out to be an enjoyable learning experience. I’ve been able to make everything work, (so far), with way less code than was needed in 2007. Of course, if your browser can’t handle the project’s Javascript requirements the JS is not loaded at all and you get the plain HTML experience, which isn’t so bad either.

For more on choosing not to burden your users and customers with unneeded slowness, see the ALA article Choosing Vanilla Javascript, which is 15 months old now, and things have just gotten better since it was published!

Historical & Future Writing Patterns

Let’s have a look at the what content has been the most popular here on johnbeales.com over the past several years, what I’ve written the most of, and what I’m hoping to write more of, (this is part of the 10 Days to a Better Blog series I wrote about on Sunday, and is a bit introspective).

The two posts that are by far the most popular are ancient: Using VLC to transcode an Axis Camera’s video stream, and stream it out again from 2008, and Transferring OS X and Boot Camp to a New Hard Drive from 2011. In the case of the streaming post, transcoding or transforming video streams from IP cameras for public viewing on the web was a new concept, using VLC, which is free, to do it was very attractive, and there was very little information available on the web about how to turn the stream from an IP camera into something consumable in a web browser. As for the post about transferring to a new hard drive, the post is a detailed step-by-step, and there’s a large audience of people who buy new macs and want to transfer their info. These are one-hit-wonders, though, I could update them, but they would no longer be new. In the case of streaming the answer was “Use Wowza” even when I wrote the post.

Let’s look at content categories that have done well. “How To” content is popular, probably because that’s most of what’s here, but things I write about most often, like WordPress and Javascript, are not consistent leaders. Some WordPress posts have good traffic numbers, but it’s the weird posts like Improving Trac’s Tickets by Milestone Report or How to Update an Updated Subversion Repository from a Working Copy that have generated the most comments, excluding the two hero posts discussed above.

I’ll keep writing How To content for myself, I have some sketched out already, but I should explore writing about weird things a bit more. There are a couple of new categories that might show up here as well: Comment on social issues, (I touched on exclusion of women on Monday), and sometimes Photography, which used to be a lot more active than it is.