Your requirements could not be resolved to an installable set of packages. Problem 1 - Conclusion: don't install phpspec/phpspec 2.5.6 (conflict analysis result) - Conclusion: don't install phpspec/phpspec 2.5.x-dev (conflict analysis result) - Conclusion: don't install symfony/process v3.4.47 (conflict analysis result) - Root composer.json requires phpspec/phpspec ~2.0,>=2.4@dev -> satisfiable by phpspec/phpspec[2.4.0-alpha1, ..., 2.5.x-dev]. - Conclusion: don't install symfony/process[v3.2.14] | install symfony/process[v5.4.28] (conflict analysis result) - Conclusion: don't install symfony/process v5.4.28 (conflict analysis result) - Conclusion: don't install symfony/process v3.3.6 (conflict analysis result) - Root composer.json requires kphoen/rusty dev-master -> satisfiable by kphoen/rusty[dev-master]. - kphoen/rusty dev-master requires symfony/process ^4.4|^5.0 -> satisfiable by symfony/process[v4.4.0, ..., v4.4.44, v5.0.0, ..., v5.4.28]. - You can only install one version of a package, so only one of these can be installed: symfony/process[v2.3.0, ..., v2.8.52, v3.0.0, ..., v3.4.47, v4.0.0, ..., v4.4.44, v5.0.0, ..., v5.4.28, v6.0.0, ..., v6.4.0, v7.0.0]. - phpspec/phpspec[2.4.0-alpha1, ..., 2.5.5] require symfony/process ^2.6|~3.0 -> satisfiable by symfony/process[v2.6.0, ..., v2.8.52, v3.0.0, ..., v3.4.47]. - Conclusion: don't install symfony/process v2.8.52 (conflict analysis result)