Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires maglnet/composer-require-checker ^4.18.0 -> satisfiable by maglnet/composer-require-checker[4.18.0, 4.19.0]. - azjezz/psl[3.2.0, ..., 3.3.0, 4.2.0] require ext-intl * -> it is missing from your system. Install or enable PHP's intl extension. - maglnet/composer-require-checker 4.18.0 requires azjezz/psl ^3.2.0 -> satisfiable by azjezz/psl[3.2.0, 3.3.0]. - maglnet/composer-require-checker 4.19.0 requires azjezz/psl ^4.2.0 -> satisfiable by azjezz/psl[4.2.0]. To enable extensions, verify that they are enabled in your .ini files: - C:\tools\php\php.ini You can also run `php --ini` in a terminal to see which files are used by PHP in CLI mode. Alternatively, you can run Composer with `--ignore-platform-req=ext-intl` to temporarily ignore these required extensions.