Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires phpstan/phpstan ^1.11 -> satisfiable by phpstan/phpstan[1.11.0, ..., 1.11.9]. - phpstan/phpstan[1.11.0, ..., 1.11.9] require php ^7.2|^8.0 -> your php version (7.1.33) does not satisfy that requirement.