PHP Intl extension #45613

You need to install / enable the intl extension.
To to that you need to refer to the documation of you PHP provider.

For example, if you used wamp, and IIRC you can right click on the icon > extension > intl
If you use wsl with ubuntu/debian : something like sudo apt install php-intl

I had to do two things on my Symfony 6.1 project to make this work:

1. change Dockerfile to install Intl extension (although is was already in there)
2. install symfony/intl via docker after rebuild of image

Dockerfile changes:
FROM

# persistent / runtime deps
RUN apk add --no-cache \
		acl \
		fcgi \
		file \
		gettext \
		git \
	;

RUN set -eux; \
    install-php-extensions \
    	intl \
    	zip \
    	apcu \
	opcache \
    ;

TO

# persistent / runtime deps
RUN apk add --no-cache \
		acl \
		fcgi \
		file \
		gettext \
		git \
		icu-dev \
	;

RUN set -eux; \
    install-php-extensions \
    	zip \
    	apcu \
	opcache \
    ;

RUN docker-php-ext-configure intl && \
	docker-php-ext-install intl \
	;

Then, after rebuild of the image, run this in the container:
composer require symfony/intl