Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires phpunit/phpunit ^9.6.21 -> satisfiable by phpunit/phpunit[9.6.21, 9.6.x-dev]. - Root composer.json requires infection/infection ^0.29.7 -> satisfiable by infection/infection[0.29.7, 0.29.x-dev]. - vimeo/psalm 5.x-dev requires nikic/php-parser ^4.17 -> satisfiable by nikic/php-parser[v4.17.0, ..., 4.x-dev]. - Conclusion: don't install one of nikic/php-parser[v5.3.1], vimeo/psalm[5.26.1] | install nikic/php-parser[v4.17.0] (conflict analysis result) - You can only install one version of a package, so only one of these can be installed: nikic/php-parser[v4.17.0, ..., 4.x-dev, v5.0.0alpha1, ..., v5.3.1]. - Conclusion: install nikic/php-parser v5.3.1 (conflict analysis result) - Root composer.json requires vimeo/psalm ^5.26.1 -> satisfiable by vimeo/psalm[5.26.1, 5.x-dev]. Use the option --with-all-dependencies (-W) to allow upgrades, downgrades and removals for packages currently locked to specific versions.