Error when using composer require-dev.mikey179/vfsStream is invalid

Question

I am using Amazon LightSail and the CodeIgniter framework. Trying to install PhpSpreadsheet - https://phpspreadsheet.readthedocs.io/en/latest/#installation using

composer require phpoffice/phpspreadsheet

However I then am greeted with

 [RuntimeException]
  require-dev.mikey179/vfsStream is invalid, it should not contain uppercase characters. Please use mikey179/vfsstream instead.

I did the usual Googling but couldn't find anything specific.

When I run

composer.phar show

I get the error from above.

Answer 1

You must have mikey179/vfsStream in your composer.json in require-dev section (as the problem is for require-dev and you are trying to do normal require).

Simply change the name of package to all lowercase characters.