[php-src] Issue #18831: Build fails with ICU 76+ due to missing `toU16StringView` in unistr.h

Issue: https://github.com/php/php-src/issues/18831 Author: thecaliskan ### Description I'm encountering a build failure when trying to install PHP extensions (intl) on Alpine 3.22. The issue is caused by the toU16StringView function being used in ICU headers but missing from the current ICU version shipped with Alpine 3.22 (ICU 76+). ## 📄 Error Log ``` /usr/include/unicode/unistr.h: In function 'icu_76::UnicodeString icu_76::operator+(const UnicodeString&, const S&)': /usr/include/unicode/unistr.h:4118:46: error: 'toU16StringView' is not a member of 'icu_76::internal' 4118 | return unistr_internalConcat(s1, internal::toU16StringView(s2)); | ^~~~~~~~~~~~~~~ /usr/include/unicode/unistr.h:4118:10: error: there are no arguments to 'unistr_internalConcat' that depend on a template parameter, so a declaration of 'unistr_internalConcat' must be available [-fpermissive] ``` You can also reproduce this with a minimal Dockerfile using php:8.4-alpine3.22: ## 🐳 Docker Reproduction ```Dockerfile FROM php:8.4-alpine3.22 RUN apk add --no-cache icu-dev g++ && docker-php-ext-install intl ``` ## ✅ Works on: - Alpine 3.21 (with older ICU version) ## ❌ Fails on: - Alpine 3.22 (icu-76.1) --- This appears to be an incompatibility between PHP's use of the ICU headers and the updated ICU 76+ API. toU16StringView might have been removed or renamed (e.g., to toU16StringViewNullable). Would love guidance on how best to proceed. Is a patch to intl needed to be compatible with ICU 76+? Thanks! > Reference Issue: [GitHub Issue Link](https://github.com/php/php-src/issues/18743) > Reference build failure: [GitHub Action > Link](https://github.com/thecaliskan/oort/actions/runs/15573866767/job/43865059489) ### PHP Version ```plain 8.4-alpine 8.3-alpine 8.2-alpine 8.1-alpine ``` ### Operating System Alpine 3.22