Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires simplesamlphp/xml-security ^0.6.6 -> satisfiable by simplesamlphp/xml-security[v0.6.6]. - simplesamlphp/xml-security v0.6.6 requires simplesamlphp/assert ^0.8.0 -> found simplesamlphp/assert[v0.8.0] but it conflicts with your root composer.json require (^1.0.0).