Your requirements could not be resolved to an installable set of packages. Problem 1 - vimeo/psalm[5.15.0, ..., 5.23.1] require nikic/php-parser ^4.16 -> satisfiable by nikic/php-parser[v4.16.0, ..., v4.19.1]. - vimeo/psalm 4.30.0 requires nikic/php-parser ^4.13 -> satisfiable by nikic/php-parser[v4.13.0, ..., v4.19.1]. - You can only install one version of a package, so only one of these can be installed: nikic/php-parser[v4.10.0, ..., v4.19.1, v5.0.0, v5.0.1, v5.0.2]. - infection/infection 0.28.1 requires nikic/php-parser ^5.0 -> satisfiable by nikic/php-parser[v5.0.0, v5.0.1, v5.0.2]. - Root composer.json requires infection/infection 0.28.1 -> satisfiable by infection/infection[0.28.1]. - Root composer.json requires vimeo/psalm ^4.30.0 || ^5.15 -> satisfiable by vimeo/psalm[4.30.0, 5.15.0, ..., 5.23.1]. Use the option --with-all-dependencies (-W) to allow upgrades, downgrades and removals for packages currently locked to specific versions.