Re: Long-Term Planning for PHP 9.0 Error Promotion

On 25-01-2022 00:47, Mark Randall wrote:

Internals, PHP 9.0, likely a few years away at this point, is our next opportunity to make significant breaking changes. So I thought it would be appropriate to start a thread discussing what breaking changes we might want to include in it, specifically in relation to error handling behaviour both at engine level, and potentially library level.

Recently I came across the following array destructuring edge case:

    [$a, $b] = 1;

This statement is perfectly valid. No exception, no error, no notice, nothing. Its effect is that it assigns null to both variables. IMHO the above should be a compile time error. Also, I think the following should throw a TypeError when the right hand side is not iterable:

    [$a, $b] = $c;

Currently, the above statement silently assigns null to both $a and $b. In the context of a foreach loop, the behavior is slightly better. The following generates a warning:

    foreach (1 as [$b, $c]);

As does the following if $a is not iterable:

    foreach ($a as [$b, $c]);

As array destructuring is conceptually related to array unpacking I would expect the engine to handle similar cases in the same way. This is not the case though. The following statement throws a TypeError since PHP 8.0:

    var_dump(...1);

And, while we are at it, the following is a fatal error:

    $a = [...1];

while the following throws an Error exception (should be TypeError?) when $b is not iterable:

    $a = [...$b];

Perhaps these oddities / inconsistencies are good candidates for addressing in PHP 9.0? Regards, Dik Takken