PHP REQUIREMENT LINK : http://codeigniter.com/user_guide/intro/requirements.html and also README.md(PHP 8.1 is required since Codeigniter 4.5.0 )
Download the package using composer. (Since 4.0.4) - php composer.phar create-project codeigniter4/appstarter /{{PATH}}/{{TO}}/{{CODEIGNITER_DIRECTORY}}
