Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires psalm/plugin-phpunit ^0.18.4 -> satisfiable by psalm/plugin-phpunit[0.18.4]. - Conclusion: don't install nikic/php-parser v4.17.1 (conflict analysis result) - Conclusion: don't install nikic/php-parser v4.16.0 (conflict analysis result) - Conclusion: don't install vimeo/psalm 5.19.0 (conflict analysis result) - Root composer.json requires phpunit/phpunit ^11.0 -> satisfiable by phpunit/phpunit[11.0.0, ..., 11.4.1]. - Root composer.json requires vimeo/psalm ^5.19 -> satisfiable by vimeo/psalm[5.19.0, ..., 5.26.1]. - Conclusion: don't install vimeo/psalm[5.22.0] | install one of nikic/php-parser[v4.16.0, v4.17.1, v4.19.0] (conflict analysis result) - Conclusion: don't install vimeo/psalm[5.19.1] | install one of nikic/php-parser[v4.16.0, v4.17.1, v4.19.0] (conflict analysis result) - Conclusion: don't install nikic/php-parser v4.19.0 (conflict analysis result) - psalm/plugin-phpunit 0.18.4 requires vimeo/psalm dev-master || dev-4.x || ^4.7.1 || ^5@beta || ^5.0 -> satisfiable by vimeo/psalm[5.19.0, ..., 5.26.1]. - vimeo/psalm[5.20.0, ..., 5.26.1] conflict with nikic/php-parser v4.17.0. - Conclusion: install one of vimeo/psalm[5.19.0, 5.19.1, 5.22.0], nikic/php-parser[v4.16.0, v4.17.0, v4.17.1, v4.19.0] (conflict analysis result) Use the option --with-all-dependencies (-W) to allow upgrades, downgrades and removals for packages currently locked to specific versions.