Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires simplesamlphp/simplesamlphp ^2.6@dev -> satisfiable by simplesamlphp/simplesamlphp[2.6.x-dev (alias of dev-simplesamlphp-2.6)]. - simplesamlphp/simplesamlphp[dev-simplesamlphp-2.6, 2.6.x-dev] require simplesamlphp/assert ~2.0 -> found simplesamlphp/assert[v2.0.0, v2.0.1, v2.0.2] but it conflicts with your root composer.json require (~3.0). - simplesamlphp/simplesamlphp 2.6.x-dev is an alias of simplesamlphp/simplesamlphp dev-simplesamlphp-2.6 and thus requires it to be installed too.