You may use it to help you compile the list of extensions you use and require. The show –platform command lists all PHP extensions available on your system.
Failure to list required PHP extensions may lead to a bad user experience: Composer will install your package without any errors but it will then fail at run-time. Not all PHP installations are created equal: some may miss extensions you may consider as standard (such as ext-mysqli which is not installed by default in Fedora/CentOS minimal installation systems). It is important to list PHP extensions your project requires. The best explanation why listing required extensions is a good idea comes from Composer itself:
The new Extension is missing in composer.json inspection will detect the usages of functions, constants, and classes that rely on PHP extensions not currently listed in composer.json.
The new inspections will detect extensions that are not listed in composer.json, highlight the non-canonical order of elements in PHPDoc annotations, and warn you when an optional parameter is used in a method declaration before the required one. Every PhpStorm release brings new inspections among other features, and PhpStorm 2018.2 is no exception.
