Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires simplesamlphp/saml11 ~1.2.5 -> satisfiable by simplesamlphp/saml11[v1.2.5]. - simplesamlphp/saml11 v1.2.5 requires simplesamlphp/xml-common ~1.24.0 -> found simplesamlphp/xml-common[v1.24.0, v1.24.1, v1.24.2] but it conflicts with your root composer.json require (~2.0.0). Problem 2 - Root composer.json requires simplesamlphp/simplesamlphp ~2.4.2 -> satisfiable by simplesamlphp/simplesamlphp[v2.4.2, v2.4.3]. - simplesamlphp/saml2[v5.0.0, ..., v5.0.1] require simplesamlphp/xml-common ^1.16 -> found simplesamlphp/xml-common[v1.16.0, ..., v1.26.0] but it conflicts with your root composer.json require (~2.0.0). - simplesamlphp/saml2[v5.0.2, ..., v5.0.4] require simplesamlphp/xml-common ~1.25.0 -> found simplesamlphp/xml-common[v1.25.0, v1.25.1] but it conflicts with your root composer.json require (~2.0.0). - simplesamlphp/simplesamlphp v2.4.2 requires simplesamlphp/saml2 ^5.0.0 -> satisfiable by simplesamlphp/saml2[v5.0.0, ..., v5.0.4]. - simplesamlphp/simplesamlphp v2.4.3 requires simplesamlphp/xml-common ^1.24.2 -> found simplesamlphp/xml-common[v1.24.2, v1.25.0, v1.25.1, v1.26.0] but it conflicts with your root composer.json require (~2.0.0).