Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires phpstan/phpstan-deprecation-rules ^2 -> satisfiable by phpstan/phpstan-deprecation-rules[2.0.0, 2.0.1]. - phpstan/phpstan-deprecation-rules[2.0.0, ..., 2.0.1] require php ^7.4 || ^8.0 -> your php version (7.1.33) does not satisfy that requirement.