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Last time, I talked about fun uses of the match() expression in PHP, using unconventional types of expressions on the right-arm branch. This time, I want to expand that discussion to include fun tricks on the left-side of the =>, and how you can easily match by multiple values at the same time.

I'm going to assume you have read the previous installment about how match() works and what an "expression" means. Also, I don't claim to be the original source of these tricks. I'm just documenting them because they're cool. Let's dive in.

Recently, I've been helping a new developer out in a chat room. He's still learning PHP and working through tutorials, with lots of questions along the way. Earlier this week, by accident, he stumbled across a use of match() statements I'd not considered before. While technically not right for his use case, it did suggest another, potentially valid use for match() I'd not seen. Let's add it to the list of cool things you can do with match().

This is old-hat to some people, but it's still a nice trick.

PHP has long supported Java-esque property and method access control. Object properties and methods may be marked public, protected, or private to control what other code may access them. The general recommendation for years is that properties should be non-public in almost all cases, unless you're using the new readonly flag in PHP 8.1.

(There's a good case to be made that object-level encapsulation is the wrong model in the first place, and package-level visibility is the superior model. I happen to agree with that argument, but that's neither here nor there for the time being.)

Most of the time, you want to respect the visibility set by the code's author. It's telling you how an object should be used, and if you do otherwise you're on your own. However, there are cases in meta-programming situations where you need to be able to bypass the visibility in order to manipulate the state of an object in a dynamic fashion. The most common scenarios are serialization, de-serialization, hydration from an ORM, and similar.

I am apparently late in coming to this trick, but PHP 8.1 is going to make it even nicer to use.

A clever trick

There's an interesting intersection of functionality in PHP:

• Declared object properties are more efficient than dynamic ones, because the engine can make assumptions about what data type to expect.
• The magic __get() and __set() methods trigger when there is no property with a given name that has been set.
• Fun fact: A property that has been declared but not initialized with a value is still technically "set"... to uninitialized.
• However, you can unset() an uninitialized property.

That means you can do clever tricks like this (and some systems do, internally):