Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires nettrine/extra ^0.1.0 -> satisfiable by nettrine/extra[v0.1.0]. - Root composer.json requires nettrine/fixtures ^0.8.0 -> satisfiable by nettrine/fixtures[v0.8.0]. - Root composer.json requires nettrine/orm ^0.9.0 -> satisfiable by nettrine/orm[v0.9.0]. - nettrine/extra v0.1.0 requires doctrine/orm ^2.16.0 -> satisfiable by doctrine/orm[2.16.0, ..., 2.21.x-dev]. - nettrine/fixtures v0.8.0 requires doctrine/orm ^3.3.0 -> satisfiable by doctrine/orm[3.3.0, ..., 3.7.x-dev]. - Conclusion: don't install doctrine/orm 2.17.5 (conflict analysis result) - Conclusion: don't install doctrine/orm 2.20.8 (conflict analysis result) - Conclusion: don't install doctrine/orm 2.20.9 (conflict analysis result) - Conclusion: don't install doctrine/orm 3.6.2 (conflict analysis result) - You can only install one version of a package, so only one of these can be installed: doctrine/orm[2.14.0, ..., 2.21.x-dev, 3.3.0, ..., 3.7.x-dev]. Use the option --with-all-dependencies (-W) to allow upgrades, downgrades and removals for packages currently locked to specific versions.