Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires phpcsstandards/php_codesniffer dev-master -> satisfiable by phpcsstandards/php_codesniffer[dev-master]. - roave/security-advisories dev-master conflicts with squizlabs/php_codesniffer >=1,<2.8.1|>=3,<3.0.1 (phpcsstandards/php_codesniffer dev-master replaces squizlabs/php_codesniffer > 2.0). - Root composer.json requires roave/security-advisories dev-master -> satisfiable by roave/security-advisories[dev-master].