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Date: Thu, 26 Jun 2025 10:31:55 -0400
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Subject: [PHP-DEV] Allow BcMath\Number to work identically to bcmath functions
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From: zimzat@zimzat.com (Russell Lee)

When `BcMath\Number` was introduced it allowed `string|int` method 
arguments. According to a separate RFC to allow `int` to the functions 
this was done as a performance optimization. Unfortunately this also 
means it effectively disallows `float` types because PHP will truncate 
them to integers (and emit a deprecation report) instead of preserving 
them as strings.

Example: https://3v4l.org/Bi5Kl

```php
var_dump(
     (string)new BcMath\Number(5)->sub(4.2, 1),
     bcsub(5, 4.2, 1),
);

string(3) "1.0"
string(3) "0.8"
```

Per SakiTakamachi:
 > If there is strong demand for creating the object from a `float`, it 
would be better to add support for `float` rather than removing `int` 
from the signature.
 > As with the bc functions, converting a `float` to a `string` can be 
easily handled within php-src.
 >
 > In any case, discussion on the mailing list is necessary.


I was hoping to be able to use Number as a drop-in replacement for 
various operations, especially back-of-the-napkin calculations, but this 
behavior makes it too easy to accidentally write `$number * 1.2` and get 
unexpected results.

There are many arguments that could be made that float is the wrong 
type, that it has rounding issues, and possibly other edge cases, but in 
the vast majority of cases `(string)$float` does exactly what is 
expected. The lack of a non-float decimal numeric type doesn't leave 
much room for native expression short of doing `Number((string)$i) * 
Number((string)$j)` or `Number('1.2') * '1.2'`.

The expectation is that in PHP 9.0 float-to-int will be disallowed and 
would automatically drop back to float-to-string in this case, but that 
is still a long way away and would mean being unable to recommend using 
Number in 8.4, 8.5, and beyond.

Request context and discussion:
https://github.com/php/php-src/issues/18674

BcMath\Number RFC:
https://wiki.php.net/rfc/support_object_type_in_bcmath

bcmath function int type RFC:
https://wiki.php.net/rfc/allow_int_args_to_bcmath_function