Your requirements could not be resolved to an installable set of packages. Problem 1 - phpunit/phpunit[5.7.21, ..., 5.7.27] require php ^5.6 || ^7.0 -> your php version (8.3.11) does not satisfy that requirement. - phpunit/phpunit[6.5.0, ..., 6.5.14] require php ^7.0 -> your php version (8.3.11) does not satisfy that requirement. - phpunit/phpunit[7.5.0, ..., 7.5.20] require php ^7.1 -> your php version (8.3.11) does not satisfy that requirement. - Root composer.json requires phpunit/phpunit ^5.7.21 || ^6.5 || ^7.5 -> satisfiable by phpunit/phpunit[5.7.21, ..., 5.7.27, 6.5.0, ..., 6.5.14, 7.5.0, ..., 7.5.20].