How to install PHP Intl Extension on Linux

Intl is stand for Internationalization, which allows PHP programmers to perform various locally aware operations including but not limited to formatting, transliteration, coding conversion, calendar operations, searching text boundaries and working with local identifiers, time zones etc.

sudo apt-get install php-intl

For the solid PHP version (PHP version 7.3 for example)

sudo apt-get install php7.3-intl

References:
StackOverflow
PHP.net