Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires simplesamlphp/simplesamlphp ^2.5@dev -> satisfiable by simplesamlphp/simplesamlphp[v2.5.0-rc3, ..., 2.6.0.x-dev (alias of dev-master)]. - simplesamlphp/simplesamlphp v2.5.0-rc3 requires simplesamlphp/saml2 ^5.1.0-rc1 -> found simplesamlphp/saml2[v5.1.0-rc1] but it does not match your minimum-stability. - simplesamlphp/simplesamlphp v2.5.0-rc5 requires simplesamlphp/xml-security ~2.0 -> satisfiable by simplesamlphp/xml-security[v2.3.1]. - simplesamlphp/simplesamlphp dev-master requires 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 (^1.9). - simplesamlphp/xml-security v2.3.1 requires 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 (^1.9). - simplesamlphp/simplesamlphp 2.6.0.x-dev is an alias of simplesamlphp/simplesamlphp dev-master and thus requires it to be installed too.