Using assert to fix PHPStan errors

I’ve been using more and more PHPStan recently and it’s been a real pleasure to improve my codebases.

Being strict is nice, but sometimes it can also be inconvenient. A lot of built-in methods in php can return false. Or sometimes, you have a “mixed” result even though you know for sure it’s type.

Let’s say you have something like this:

<?php

function stringOrArray():string|array {
    $v = someMethodThatReturnMixed();
    return $v;
}

Of course, you can do this:

function stringOrArray():string|array {
    $v = someMethodThatReturnMixed();
    if(is_string($v) || is_array($v)) {
        return $v;
    }
    throw new Exception("Invalid type");
}

But this means adding an if. Throwing an Exception. Not a big deal by itself, but if you have to fix hundreds of lines like this, it’s not great.

A quick(er) fix, is this:

function stringOrArray():string|array {
    $v = someMethodThatReturnMixed();
    assert(is_string($v)||is_array($v));
    return $v;
}

Aaaaand… done! I really like using assert : it adds type checks during development, and is ignored at no performance cost in production. And if somehow, as a developer, you made a mistake, it’s very likely you are going to catch the AssertionException that gets thrown.

That’s all for today, I hope you liked my little tip :)