Errors about array offsets

[kAlvaro]

I have an HTML form where I build a set of checkboxes from two arrays:

<input type="checkbox" name="selection[0][0]"  value="1">
<input type="checkbox" name="selection[0][1]"  value="1">
[...]

To cater with the fact that unchecked checkboxes are not sent by the browser, when I process the form I first build a normalised two-dimension array with the appropriate boolean values, and then base all my logic on that.

No matter what I do, PHPStan will always complain. In the full original code:

Offset 0|1|2|3|4|5|6|7|8|9|10|11 might not exist on non-empty-array{0?: bool, 1?: bool, 2?: bool, 3?: bool, 4?: bool, 5?: bool, 6?: bool, 7?: bool, ...}.

In a simplified version I've prepared to diagnose and share:

<?php declare(strict_types = 1);

$from = ['a', 'b', 'c'];
$to = ['a', 'b', 'c', 'd', 'd'];

/** @var array<int, array<int, bool>> $normalizedSelection */ // <- My attempt to fix linter errors
$normalizedSelection = [];
foreach ($from as $i => $f) {
	foreach ($to as $j => $t) {
		$normalizedSelection = false;
	}
}

foreach ($from as $i => $f) {
	foreach ($to as $j => $t) {
		if (!$normalizedSelection[$i][$j]) { // <-- Both errors here
			continue;
		}
	}
}

Cannot access offset 0|1|2 on false.

Cannot access offset 0|1|2|3|4 on mixed.

Is there a bug in my code? I'm reluctant to think there' a bug in PHPStan, because it looks like a very simple scenario to me.

[ondrejmirtes]

Please show the behaviour on phpstan.org/try.

[kAlvaro]

@ondrejmirtes Ah, sorry, I hadn't noticed the Share button: https://phpstan.org/r/60a0e15f-51a4-441c-8e87-3f1e65633450

[ondrejmirtes]

Well this is certainly wrong, isn’t it:

$normalizedSelection = false;

Did you mean:

$normalizedSelection[$i][$j] = false;

[kAlvaro]

Drat... I messed it up 😬. I meant this:

https://phpstan.org/r/57a1f4ed-fc50-43df-a447-753906394b19

[ondrejmirtes]

These errors are only reported with reportPossiblyNonexistentGeneralArrayOffset: true.

It’s not obvious to PHPStan you’re iterating over the same keys that were used to create the array.

[kAlvaro]

Understood. I had assumed it was actually detecting missing keys, but it's only a generic warning about a potential situation. Thank you!