Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires phpunit/phpunit ^11.0.0 -> satisfiable by phpunit/phpunit[11.0.0]. - phpunit/phpunit 11.0.0 requires php >=8.2 -> your php version (8.1.27) does not satisfy that requirement. Problem 2 - php-mock/php-mock-phpunit 2.6.1 requires phpunit/phpunit ^6 || ^7 || ^8 || ^9 -> found phpunit/phpunit[6.0.0, ..., 6.5.14, 7.0.0, ..., 7.5.20, 8.0.0, ..., 8.5.36, 9.0.0, ..., 9.6.16] but it conflicts with your root composer.json require (^11.0.0). - php-mock/php-mock-phpunit 2.7.0 requires phpunit/phpunit ^6 || ^7 || ^8 || ^9 || ^10 -> found phpunit/phpunit[6.0.0, ..., 6.5.14, 7.0.0, ..., 7.5.20, 8.0.0, ..., 8.5.36, 9.0.0, ..., 9.6.16, 10.0.0, ..., 10.5.9] but it conflicts with your root composer.json require (^11.0.0). - php-mock/php-mock-phpunit[2.7.1, ..., 2.9.0] require phpunit/phpunit ^6 || ^7 || ^8 || ^9 || ^10.0.17 -> found phpunit/phpunit[6.0.0, ..., 6.5.14, 7.0.0, ..., 7.5.20, 8.0.0, ..., 8.5.36, 9.0.0, ..., 9.6.16, 10.0.17, ..., 10.5.9] but it conflicts with your root composer.json require (^11.0.0). - Root composer.json requires php-mock/php-mock-phpunit ^2.6.1 -> satisfiable by php-mock/php-mock-phpunit[2.6.1, ..., 2.9.0]. Use the option --with-all-dependencies (-W) to allow upgrades, downgrades and removals for packages currently locked to specific versions.