Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires php ^5.6|^7.0 but your php version (8.1.2) does not satisfy that requirement. Problem 2 - phpunit/phpunit[5.7.0, ..., 5.7.27] require php ^5.6 || ^7.0 -> your php version (8.1.2) does not satisfy that requirement. - phpunit/phpunit[6.0.0, ..., 6.5.14] require php ^7.0 -> your php version (8.1.2) does not satisfy that requirement. - Root composer.json requires phpunit/phpunit ^5.7|^6.0 -> satisfiable by phpunit/phpunit[5.7.0, ..., 5.7.27, 6.0.0, ..., 6.5.14].