Allow number_format to be only passed 3 arguments

[Girgias]

Should I also drop the PHPAPI _php_math_number_format() function?

[thg2k]

I don't think taking null as default is appropriate here, 3 and 4 are string, not ?string, and it would not be consistent with the other builtins. Default keyword, anyone?

[Girgias]

I don't think taking null as default is appropriate here, 3 and 4 are string, not ?string, and it would not be consistent with the other builtins. Default keyword, anyone?

PHP 7.4 already accepts null as can be seen here: https://heap.space/xref/PHP-7.4/ext/standard/math.c?r=d90cdbd9#1261

This is even easier to see by looking at it's signature from the stubs, the source of truth, which is function number_format(float $number, int $decimals = 0, ?string $decimal_point = "." , ?string $thousands_separator = ","): string {}

Anyway the default keyword thing is completely useless since we got named arguments in PHP 8.0 and moreover null is the correct semantics to get the default behaviour.

About the "inconsistency" in regards to other built-in functions. We are making the arguments of other built-in functions nullable because what happens in effect is function overloading which is only possible for internal functions and we want to align internal and userland behaviour.

Therefore could you please do some research into the various changes made in the engine for this major version before coming up with a supposedly solution which has already been declined in the past, see https://wiki.php.net/rfc/skipparams

[nikic]

@Girgias We do try to avoid nullability if there is a possibility to write the default value explicitly -- which there is in this case. Unfortunately the nullability support is preexisting, so dropping it is a BC break. Maybe the fact that null support is not documented gives us the necessary leeway to do that?

[nikic]

On the other hand, it looks like null support in this function is really old: 6d7cac7 I don't thin it's worth breaking functionality that has existed since 2004 and doesn't really cost us to maintain.