Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires phpunit/phpunit ^9.0 -> satisfiable by phpunit/phpunit[9.0.0, ..., 9.6.x-dev]. - humbug/box 4.5.1 requires symfony/console ^6.1.7 -> found symfony/console[v6.1.7, ..., 6.4.x-dev] but these were not loaded, likely because it conflicts with another require. - humbug/box 4.6.0 requires symfony/filesystem ^6.1.5 -> found symfony/filesystem[v6.1.5, ..., 6.4.x-dev] but these were not loaded, likely because it conflicts with another require. - humbug/box 4.x-dev is an alias of humbug/box dev-main and thus requires it to be installed too. - humbug/box[dev-main, 4.6.1, ..., 4.x-dev] require sebastian/diff ^5.0 -> satisfiable by sebastian/diff[5.0.0, ..., 5.1.x-dev]. - Conclusion: don't install sebastian/diff 5.1.0 (conflict analysis result) - Root composer.json requires humbug/box ^4.5.1 -> satisfiable by humbug/box[4.5.1, 4.6.0, 4.6.1, 4.x-dev (alias of dev-main)]. Use the option --with-all-dependencies (-W) to allow upgrades, downgrades and removals for packages currently locked to specific versions.