Your requirements could not be resolved to an installable set of packages.
Problem 1
- Conclusion: don't install phpunit/phpunit 11.2.6 (conflict analysis result)
- vimeo/psalm[5.0.0, ..., 5.13.1] require php ^7.4 || ~8.0.0 || ~8.1.0 || ~8.2.0 -> your php version (8.3.9) does not satisfy that requirement.
- sebastian/diff[4.0.0, ..., 4.0.1] require php ^7.3 -> your php version (8.3.9) does not satisfy that requirement.
- vimeo/psalm[5.22.0, ..., 5.25.0] require nikic/php-parser ^4.16 -> satisfiable by nikic/php-parser[v4.16.0, ..., v4.19.1].
- You can only install one version of a package, so only one of these can be installed: nikic/php-parser[v4.13.0, ..., v4.19.1, v5.0.0, v5.0.1, v5.0.2, v5.1.0].
- vimeo/psalm[5.14.0, ..., 5.21.1] require sebastian/diff ^4.0 || ^5.0 -> satisfiable by sebastian/diff[4.0.0, ..., 4.0.6, 5.0.0, ..., 5.1.1].
- phpunit/php-code-coverage[11.0.0, ..., 11.0.5] require nikic/php-parser ^5.0 -> satisfiable by nikic/php-parser[v5.0.0, v5.0.1, v5.0.2, v5.1.0].
- You can only install one version of a package, so only one of these can be installed: sebastian/diff[4.0.0, ..., 4.0.6, 5.0.0, ..., 5.1.1, 6.0.0, 6.0.1, 6.0.2].
- phpunit/phpunit[11.2.0, ..., 11.2.2] require phpunit/php-code-coverage ^11.0 -> satisfiable by phpunit/php-code-coverage[11.0.0, ..., 11.0.5].
- phpunit/phpunit[11.2.0, ..., 11.2.2] require sebastian/diff ^6.0 -> satisfiable by sebastian/diff[6.0.0, 6.0.1, 6.0.2].
- Root composer.json requires phpunit/phpunit ^11.2 -> satisfiable by phpunit/phpunit[11.2.0, ..., 11.2.6].
- Root composer.json requires vimeo/psalm ^5.0 -> satisfiable by vimeo/psalm[5.0.0, ..., 5.25.0].