negative powers() do not raise a DivisionByZeroError

[exakat]

Description

Raising to a negative power is similar to a division, so applying those to 0 should raise a DivisionByZeroError

The following code:

<?php

echo 0 ** -1;
echo 0 ** -2;
echo pow(0, -4);

Resulted in this output:

INF
INF
INF

But I expected this output instead:

PHP Fatal error:  Uncaught DivisionByZeroError: Division by zero

PHP Version

8.1.2

Operating System

N/A

[iluuu1994]

I think it makes sense to throw a DivisionByZeroError here but I'm not sure if it shouldn't rather be classified as a feature since this has been like this forever and likely would break some code out there.

[cmb69]

Also, this might need special casing, at least for doubles, since that just calls pow(3) which may set errno or not (with Visual Studio, it does not).

[drealecs]

Keep in mind that INF also makes sense for some cases and was only changed to DivisionByZeroError in PHP 8.0 (https://wiki.php.net/rfc/engine_warnings#division_by_zero).
Before that, in PHP 7, it was a warning.

If changed, I believe it should be done by using the RFC process, making it first a warning and only from PHP 9.0 an error.

[iluuu1994]

I create a PoC here. master...iluuu1994:php-src:throw-division-by-zero-on-pow-of-base-0-exponent-lt-eq-0

Mathematically the current behavior is incorrect. I think it makes sense to correct this so I'll propose an RFC. The current implementation throws a hard error but we'll need an implementation that just throws a deprecation. That should be a small change though.