Could not find package codeigniter4/framework with stability stable
You may install develop branch by:
composer create-project codeigniter4/framework:dev-develop
Codeigniter 4 Moved to Production and also updated documentation in Feb 24,2020 you should try this code in composer
composer create-project codeigniter4/appstarter project-rootCheck the latest documentation Codeigniter4 Documentation
It looks like your PHP version is older than required in codeigniter4. please check whether your PHP version is 7.2(or higher) or not. if you're running below 7.2 version of PHP you'll not be able to use codeigniter4.