Your requirements could not be resolved to an installable set of packages. Problem 1 - phpunit/phpunit[5.5.0, ..., 5.7.27] require php ^5.6 || ^7.0 -> your php version (8.1.27) does not satisfy that requirement. - phpunit/php-token-stream[1.3.0, ..., 1.4.12] require ext-tokenizer * -> it is missing from your system. Install or enable PHP's tokenizer extension. - phpunit/phpunit[6.5.0, ..., 6.5.14] require php ^7.0 -> your php version (8.1.27) does not satisfy that requirement. - phpunit/phpunit[7.5.0, ..., 7.5.20] require php ^7.1 -> your php version (8.1.27) does not satisfy that requirement. - phpunit/phpunit[9.0.0, ..., 9.2.6] require php ^7.3 -> your php version (8.1.27) does not satisfy that requirement. - phpunit/phpunit[9.3.0, ..., 9.6.17] require ext-xml * -> it is missing from your system. Install or enable PHP's xml extension. - phpunit/phpunit 4.8.36 requires phpunit/php-code-coverage ~2.1 -> satisfiable by phpunit/php-code-coverage[2.1.0, ..., 2.2.4]. - phpunit/php-code-coverage[2.1.0, ..., 2.2.4] require phpunit/php-token-stream ~1.3 -> satisfiable by phpunit/php-token-stream[1.3.0, ..., 1.4.12]. - Root composer.json requires phpunit/phpunit ^4.8.36 || ^5.5 || ^6.5 || ^7.5 || ^9.0 -> satisfiable by phpunit/phpunit[4.8.36, 5.5.0, ..., 5.7.27, 6.5.0, ..., 6.5.14, 7.5.0, ..., 7.5.20, 9.0.0, ..., 9.6.17]. To enable extensions, verify that they are enabled in your .ini files: - /etc/php/8.1/cli/php.ini - /etc/php/8.1/cli/conf.d/20-curl.ini - /etc/php/8.1/cli/conf.d/20-dom.ini - /etc/php/8.1/cli/conf.d/20-mbstring.ini - /etc/php/8.1/cli/conf.d/20-phar.ini - /etc/php/8.1/cli/conf.d/20-xmlwriter.ini - /etc/php/8.1/cli/conf.d/99-pecl.ini You can also run `php --ini` in a terminal to see which files are used by PHP in CLI mode. Alternatively, you can run Composer with `--ignore-platform-req=ext-tokenizer --ignore-platform-req=ext-xml` to temporarily ignore these required extensions.