Throw exception for invalid characters for number base

[Sjord]

This is about the situation where a character is not within the specified number base. E.g. only 0-9, a-f are allowed for hexadecimal, so what should hexdec('z') do?

In the past, such characters were silently ignored. Since PHP 7.4 a deprecation notice would be generated. This PR changes that to a ValueError Exception.

RFC: https://wiki.php.net/rfc/throw_error_for_invalid_characters_for_number_base
Earlier RFC: https://wiki.php.net/rfc/base_convert_improvements

[devnexen]

Hi @Sjord. My main concern is process about your PR is effectively phase 2 of the 2018 base_convert_improvements RFC (the 8.0 exception that never shipped),
so a throw in 8.6 likely needs fresh cover. The natural home is the grouped rfc/php86_valueerror_conversions work; folding the four base functions in there, or
floating it on the list first, would keep things consistent.

It also overlaps your own precision-loss thread; both touch _php_math_basetozval, better designed together.

[Sjord]

I added it to the RFC: https://wiki.php.net/rfc/php86_valueerror_conversions#throw_error_for_invalid_characters_for_number_base

[Sjord]

I also mailed the internals mailing list:

Functions that convert from one number base to another should only accept characters valid in that number base. E.g. only 0-9, a-f are allowed for hexadecimal, so what should hexdec('z') do?

In the past, such characters were silently ignored. Since PHP 7.4 a deprecation notice would be generated, as a result of this RFC: https://wiki.php.net/rfc/base_convert_improvements. That RFC also proposed throwing an exception as of PHP 8.0, but that was never implemented. I propose to throw a ValueError for invalid characters starting in PHP 8.6. I added this to the Grouped ValueError Conversions for PHP 8.6 RFC: https://wiki.php.net/rfc/php86_valueerror_conversions#throw_error_for_invalid_characters_for_number_base

This applies to bindec, octdec, hexdec, and base_convert.

[Sjord]

PHP RFC: Throw ValueError for invalid characters in number base functions