Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires simplesamlphp/saml2 ~5.0.3 -> satisfiable by simplesamlphp/saml2[v5.0.3, v5.0.4, v5.0.5]. - simplesamlphp/saml2[v5.0.3, ..., v5.0.5] require simplesamlphp/assert ~1.8.1 -> found simplesamlphp/assert[v1.8.1, v1.8.2, v1.8.3] but it conflicts with your root composer.json require (~1.9.0).