Author: Kailey Lampert

register_setting() can be really handy, but take note! The first time your option gets saved, it’ll pass through the santize callback twice. With most input, it won’t matter; and if you’re explicit, it won’t matter either. But under the right conditions, it will.

Suppose your register_setting() looks like this:

register_setting( $option_group, 'checkbox', 'sanitize' );

And you have a pair of checkboxes like this:

<input type="checkbox" name="checkbox[one]" value="1" />
<input type="checkbox" name="checkbox[two]" value="1" />

And finally, your sanitize callback looks like this

function sanitize( $input ) {
	$input['one'] = isset( $input[ 'one' ] ) ? true : false;
	$input['two'] = isset( $input[ 'two' ] ) ? true : false;
	return $input;
}

See the problem?

On the very first save, both $input['one'] and $input['two'] will be true, no matter what. Say checkbox one is unchecked, when it fist passes through, $input['one'] is set to false – as expected. But when the input is passed through sanitize the second time, $input['one'] is set (to false) and thus the $input['one'] is changed to true.

So the moral of the story is: be more explicit, don’t make assumptions.

Suppose you want to get some information about some posts in this format: an array of post titles, keyed by the post ID. How would you do it? Spoiler alert: Skip the first 2 options

Let’s assume you’re fetching some posts via get_posts(). For simplicity I won’t be passing an arguments to that function, but go ahead if you want to 🙂

$posts = get_posts();

Option 1

$post_titles = array();

foreach( $posts as $p ) {
	$post_titles[ $p->ID] = $p->post_title;
}

Not bad, but surely there’s a WordPress-y way to do that.

Option 2

You might have come across the function wp_list_pluck() which is really neat for pulling a particular value by key from an array of arrays or objects.

$post_titles = wp_list_pluck( $posts, 'post_title' );

This works for getting the titles, but leaves us without the IDs as keys. You might extrapolate that to this

$post_titles = array_combine( wp_list_pluck( $posts, 'ID' ), wp_list_pluck( $posts, 'post_title' ) );

Now we have what we want, but that seems clunky.

Option 3 (the best!)

Since WordPress 4.0, wp_list_pluck() takes a third argument that makes it behave more like the native PHP function (since 5.5) array_column(). This third argument allows you to specify a key whose value should be used as the key of the returned array.

$post_titles = wp_list_pluck( $posts, 'post_title', 'ID' );

I was on a panel at WordCamp Seattle this last weekend on becoming a better developer. One point I repeated a few times was “read core” and a related point of “don’t rely on tutorials.”

These ideas have been circling in my head since then, so I wanted to write them down.

Are Tutorials a Problem?

Tutorials can be great for providing context for code, but they often leave the reader without the tools to work out of that context. They may come away with working code, and even be able to reuse it over and over, but often without knowing what it is they’re doing. This happened to me.

It seems to me that a lot of tutorials fall into one of three categories:

1. Installers: This is probably what irks me most. There will be a headline that looks like “How to foo bar” and the first step is “Download the Foo Bar plugin” and proceed to explain how to set up a plugin. These tutorials may be perfectly fine for helping a user solve a problem, but the title is very misleading.
2. Copy-Pasta: These often just describe a problem and offer a snippet as a solution but with little-to-no explanation.
3. Over-Simplified: These are tricky. The tutorial is often really trying to teach and does so understandably by simplifying the code to the bare-bones. But they are incomplete because they skip the ‘shoulds’ (like sanitization, and security) because they’re not ‘have tos’ so that users will end up with code that technically works but with no idea that there should be more.

I’m not sure there’s hope for the Installers. Those authors should just be more careful about picking titles. Or I should be better about detecting linkbait.

As for the other two, I won’t pretend I’ve never done those. I’m also not suggesting that they have no use, but I think there’s room for improvement.

Copy-Pasta is a great way to end up with conflicting function names, a bloated functions.php file, and/or unintended side-effects.

To me, the over-simplified ones are the most dangerous because the user doesn’t know what they’re missing. It’s like teaching someone to build a car, but never getting around to the seatbelts and windshield – they’ll get in and drive on the highway and be fine till they’re not.

Go To the Source (Code)

If you want to learn how a function really works, you’ll have to look at the source. Tutorials can provide examples of how to use a function or hook, but you’re often on your own to learn how/if you can repurpose or reuse it in a different context.

I’ve faced this personally more than once, and wrote about it.

WordPress core is neither magic nor mystery (though it can feel like it at times!). It’s full of awesome gems that you may never learn about unless you dig in.

Where do you start? Try the Code Reference and look up functions that you see in tutorials. Personally, I spend a lot of time in my xref or just straight up opening core files in my text editor.