PHP 8.1 Alpine Docker容器中NumberFormatter始终返回默认en_US区域设置问题排查

Hey there, let's break down this issue and fix it step by step!

问题回顾 #

You're running into a weird behavior with NumberFormatter in a PHP 8.1 Alpine Docker container: when you specify nl_NL as the locale, getLocale() keeps returning en_US, and the currency format doesn't match Dutch expectations (you get €1,234.57 instead of €1.234,57). Oddly enough, en_GB works perfectly fine.

Here's how you're reproducing it:

1. Spin up and enter the container:

   docker run -it --rm php:8.1-fpm-alpine /bin/ash
   

2. Install dependencies and the intl extension:

   apk update && apk add icu-dev
   docker-php-ext-configure intl && docker-php-ext-install intl
   

3. Test in PHP interactive mode:

   $formatter = new NumberFormatter('nl_NL', NumberFormatter::CURRENCY);
   echo $formatter->getLocale(); // Outputs en_US (unexpected)
   echo $formatter->format(1234.567); // Outputs €1,234.57 (unexpected)
   

Your expected outcome is:

• getLocale() returns nl_NL
• Currency formatted to Dutch standards: €1.234,57

Root Cause & Fixes #

The main issue here is that Alpine Linux's default ICU packages don't come with full locale data pre-installed. Let's fix this with a few options:

1. Install the full ICU locale data package #

The icu-dev package you installed only includes development headers, not the complete locale definitions. Install the full data package:

apk add icu-data-full

After installing this, restart your PHP process (or exit and re-enter the container) and test again. This should make nl_NL recognizable, and the currency format will switch to the Dutch style.

2. Use the full locale identifier with encoding #

Sometimes Alpine requires a more precise locale string, including the encoding. Try modifying your PHP code to use nl_NL.UTF-8 instead:

$formatter = new NumberFormatter('nl_NL.UTF-8', NumberFormatter::CURRENCY);

This often helps the ICU library correctly resolve the locale.

3. Set the system-wide locale #

If the above don't work, you can explicitly generate and set the Dutch locale at the system level:

# Install locale tools
apk add locale
# Add the Dutch locale to the generation list
echo "nl_NL.UTF-8 UTF-8" >> /etc/locale.gen
# Generate the locale
locale-gen
# Set environment variables to use Dutch locale
export LC_ALL=nl_NL.UTF-8
export LANG=nl_NL.UTF-8

Once you've done this, launch the PHP interactive shell again, and the NumberFormatter should behave as expected.

Suggestions to Improve Your Question #

To make your question even clearer for other developers, you could phrase it like this:

When using NumberFormatter with nl_NL in a PHP 8.1 Alpine Docker container, getLocale() returns en_US instead of the specified locale, and currency formatting uses US-style separators instead of Dutch ones. However, en_GB works correctly. How can I fix this?

This cuts straight to the core issue, highlighting the inconsistent behavior between locales which helps others diagnose faster.

内容的提问来源于stack exchange，提问作者Frank