php -vsudo apt install -y php8.3-intlsudo systemctl restart php8.3-fpmphp -m | grep -i intlOutput
intl
Explanation
On Ubuntu, the package name follows your PHP version: php8.3-intl for PHP 8.3, php8.2-intl for PHP 8.2. Check your version first with php -v, then restart PHP-FPM (or Apache) so the site loads the extension.
In an official Docker image, use docker-php-ext-install after installing the required system libraries (libicu-dev for intl, libzip-dev for zip).
To list loaded extensions: php -m. Note that the command line and PHP-FPM may use different php.ini files.

