Your requirements could not be resolved to an installable set of packages. Problem 1 - vimeo/psalm[5.16.0, ..., 5.21.1] require sebastian/diff ^4.0 || ^5.0 -> satisfiable by sebastian/diff[4.0.0, ..., 4.0.5, 5.0.0, ..., 5.1.0]. - You can only install one version of a package, so only one of these can be installed: sebastian/diff[4.0.0, ..., 4.0.5, 5.0.0, ..., 5.1.0, 6.0.0]. - phpunit/phpunit 11.0.0 requires sebastian/diff ^6.0 -> satisfiable by sebastian/diff[6.0.0]. - sebastian/diff[4.0.0, ..., 4.0.1] require php ^7.3 -> your php version (8.3.2) does not satisfy that requirement. - Root composer.json requires phpunit/phpunit ^11.0 -> satisfiable by phpunit/phpunit[11.0.0]. - Root composer.json requires vimeo/psalm ^5.16 -> satisfiable by vimeo/psalm[5.16.0, ..., 5.21.1]. Use the option --with-all-dependencies (-W) to allow upgrades, downgrades and removals for packages currently locked to specific versions.