Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires php-parallel-lint/php-console-highlighter ^1.0.0 -> satisfiable by php-parallel-lint/php-console-highlighter[v1.0.0]. - php-parallel-lint/php-console-highlighter v1.0.0 requires ext-tokenizer * -> it is missing from your system. Install or enable PHP's tokenizer extension. Problem 2 - Root composer.json requires squizlabs/php_codesniffer ^3.7.2 -> satisfiable by squizlabs/php_codesniffer[3.7.2, ..., 3.10.2]. - squizlabs/php_codesniffer[3.7.2, ..., 3.10.2] require ext-simplexml * -> it is missing from your system. Install or enable PHP's simplexml extension. Problem 3 - phpunit/phpunit 4.8.36 requires ext-dom * -> it is missing from your system. Install or enable PHP's dom extension. - phpunit/phpunit[5.7.21, ..., 5.7.27] require php ^5.6 || ^7.0 -> your php version (5.5.38) does not satisfy that requirement. - phpunit/phpunit[6.0.0, ..., 6.5.14] require php ^7.0 -> your php version (5.5.38) does not satisfy that requirement. - phpunit/phpunit[7.0.0, ..., 7.5.20] require php ^7.1 -> your php version (5.5.38) does not satisfy that requirement. - phpunit/phpunit[8.0.0, ..., 8.5.11] require php ^7.2 -> your php version (5.5.38) does not satisfy that requirement. - phpunit/phpunit[8.5.12, ..., 8.5.39] require php >=7.2 -> your php version (5.5.38) does not satisfy that requirement. - phpunit/phpunit[9.0.0, ..., 9.2.6] require php ^7.3 -> your php version (5.5.38) does not satisfy that requirement. - phpunit/phpunit[9.3.0, ..., 9.3.8] require php ^7.3 || ^8.0 -> your php version (5.5.38) does not satisfy that requirement. - phpunit/phpunit[9.3.9, ..., 9.6.20] require php >=7.3 -> your php version (5.5.38) does not satisfy that requirement. - yoast/phpunit-polyfills[1.0.0, ..., 1.1.2] require phpunit/phpunit ^4.8.36 || ^5.7.21 || ^6.0 || ^7.0 || ^8.0 || ^9.0 -> satisfiable by phpunit/phpunit[4.8.36, 5.7.21, ..., 5.7.27, 6.0.0, ..., 6.5.14, 7.0.0, ..., 7.5.20, 8.0.0, ..., 8.5.39, 9.0.0, ..., 9.6.20]. - Root composer.json requires yoast/phpunit-polyfills ^1 -> satisfiable by yoast/phpunit-polyfills[1.0.0, ..., 1.1.2]. To enable extensions, verify that they are enabled in your .ini files: - /usr/local/php/5.5/etc/php.ini - /usr/local/php/5.5/etc/conf.d/20-phar.ini - /usr/local/php/5.5/etc/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-simplexml --ignore-platform-req=ext-dom` to temporarily ignore these required extensions.