Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires phpunit/phpunit ^12.0 -> satisfiable by phpunit/phpunit[12.0.0]. - phpunit/phpunit 12.0.0 requires php >=8.3 -> your php version (8.1.31) does not satisfy that requirement. Problem 2 - Root composer.json requires digitalrevolution/accessorpair-constraint ^2.1.18 -> satisfiable by digitalrevolution/accessorpair-constraint[v2.1.18, ..., v2.5.0]. - digitalrevolution/accessorpair-constraint v2.1.18 requires phpunit/phpunit ^9.0 || ^10.0 -> found phpunit/phpunit[9.0.0, ..., 9.6.22, 10.0.0, ..., 10.5.45] but it conflicts with your root composer.json require (^12.0). - digitalrevolution/accessorpair-constraint[v2.2.0, ..., v2.2.1] require phpunit/phpunit ^9.0 || ^10.0 || ^11.0 -> found phpunit/phpunit[9.0.0, ..., 9.6.22, 10.0.0, ..., 10.5.45, 11.0.0, ..., 11.5.7] but it conflicts with your root composer.json require (^12.0). - digitalrevolution/accessorpair-constraint[v2.3.0, ..., v2.5.0] require phpunit/phpunit ^10.0 || ^11.0 -> found phpunit/phpunit[10.0.0, ..., 10.5.45, 11.0.0, ..., 11.5.7] but it conflicts with your root composer.json require (^12.0).