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Yoda conditions

Because I usually work with WordPress, and because coding standards are a good way of avoiding endless personal decisions that then get in the way of collaborating, I tend to follow the WordPress coding standards. You should too.

Now, there’s something that I’ve noticed when looking at core WP code, which I’d always assumed was some idiosyncrasy that the WP had settled on arbitrarily. It’s where condition expressions are written with the value being tested first, then the variable against which it’s being tested:

if ( 'value' == $var ) { [do stuff...] }

I just thought that was weird, and in the interests of readability I’ve always been doing it the other way around.

Well it turns out there’s a very good reason for this style, and they call it Yoda conditions. The reason is something we’ve all done – typing a single ‘=’ instead of a double one (‘==’). What happens then (with $var = 'value') is that the value isĀ assigned to the variable, and the expression will return the assigned value. So the supposed ‘test’ will always return something equivalent to boolean false, or true, depending on the value (in this case, any string would mean the expression evaluated to true). This can be damnably hard to debug.

So, switching the order means that if you mistype the assignment operator, the mistake will result in an attempt to assign a variable to the value – which isn’t going to happen. So the error is thrown in the right place, and you don’t lose time searching for it.

The weirdness contains wisdom after all.

A little bizarre, it is, to read. Get used to it, you will.

(Credit to the guy from the WordCamp London after party last night! I forgot your name but the tip made it.)

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