Your requirements could not be resolved to an installable set of packages. Problem 1 - phpstan/phpstan-phpunit[1.3.0, ..., 1.3.15] require php ^7.2 || ^8.0 -> your php version (7.1.33) does not satisfy that requirement. - Root composer.json requires phpstan/phpstan-phpunit ^1.3 -> satisfiable by phpstan/phpstan-phpunit[1.3.0, ..., 1.3.15].