Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires ibexa/solr 5.0.x-dev -> satisfiable by ibexa/solr[5.0.x-dev (alias of dev-main)]. - ibexa/solr dev-main requires symfony/http-kernel ^5.0 -> found symfony/http-kernel[v5.0.0, ..., v5.4.45] but it conflicts with your root composer.json require (^6.4.0). - ibexa/solr 5.0.x-dev is an alias of ibexa/solr dev-main and thus requires it to be installed too.