[PHP 8.3] Polyfill mb_str_pad()

[IonBazan]

Polyfills the mb_str_pad() function added in PHP 8.3: https://wiki.php.net/rfc/mb_str_pad

Test cases were taken from the RFC implementation and adapted to PHPUnit.

[Ayesh]

I'm sorry if I'm missing something documented elsewhere, but I wanted to ask if this should belong to Mbstring or Php83? Perhapas, before declaring polyfilled mb_str_pad, we should see if the mbstring exists either as the C extension or in the form of a polyfill by checking function_exists('mb_substr')?

[IonBazan]

Good question - I wasn't sure because we don't check it for PHP 7.2 polyfill (mb_chr and mb_ord) but we do check it for PHP 7.4 (mb_str_split):

polyfill/src/Php74/bootstrap.php

Lines 21 to 23 in 05dfdff

	if (!function_exists('mb_str_split') && function_exists('mb_substr')) {
	function mb_str_split($string, $length = 1, $encoding = null) { return p\Php74::mb_str_split($string, $length, $encoding); }
	}

I guess we can add a check for mb_substr if needed here.

[stof]

the new function should be added in 2 places

• in the php 8.3 polyfill if other mbstring functions are available
• in the mbstring polyfill (so that it is available for someone using PHP 8.3 natively without the native mbstring extension)

[IonBazan]

PHP 7.2 and 7.1 don't seem to handle UTF-32 strings correctly when mbstring is missing 🤔
@nicolas-grekas Should I skip those tests?

[nicolas-grekas]

PHP 7.2 and 7.1 don't seem to handle UTF-32 strings correctly when mbstring is missing

that's quite possible, let's skip these yes (or fix the polyfill, but nobody uses utf32 so 🤷 )

[IonBazan]

Thanks for the suggestion, @nicolas-grekas - I rebased this PR and skipped the tests for UTF-32 on PHP <7.3

[nicolas-grekas]

Thank you @IonBazan.