Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires squizlabs/php_codesniffer ^3.8.0, found squizlabs/php_codesniffer[dev-master, 3.x-dev (alias of dev-master)] but it does not match your minimum-stability. Problem 2 - Root composer.json requires phpcsstandards/phpcsutils ^1.0.9, found phpcsstandards/phpcsutils[dev-stable, dev-develop, 1.x-dev (alias of dev-stable)] but it does not match your minimum-stability. Problem 3 - Root composer.json requires phpcsstandards/phpcsdevcs ^1.1.6 -> satisfiable by phpcsstandards/phpcsdevcs[1.1.6]. - phpcsstandards/phpcsdevcs 1.1.6 requires squizlabs/php_codesniffer ^3.6.2 -> found squizlabs/php_codesniffer[3.6.2, 3.7.0, 3.7.1, 3.7.2] but it conflicts with your root composer.json require (^3.8.0). Problem 4 - Root composer.json requires phpcsstandards/phpcsdevtools ^1.2.1 -> satisfiable by phpcsstandards/phpcsdevtools[1.2.1]. - phpcsstandards/phpcsdevtools 1.2.1 requires squizlabs/php_codesniffer ^3.1.0 -> found squizlabs/php_codesniffer[3.1.0, ..., 3.7.2] but it conflicts with your root composer.json require (^3.8.0).