Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires phpunit/phpunit 4.* || 5.* || 9.* -> satisfiable by phpunit/phpunit[9.6.33, 9.6.34]. - phpunit/phpunit[9.6.33, ..., 9.6.34] require php >=7.3 -> your php version (7.2.34) does not satisfy that requirement.