Your requirements could not be resolved to an installable set of packages. Problem 1 - php-http/httplug-bundle is present at version dev-4c45691754aaf8d082ab65f1356eba523f210b11 and cannot be modified by Composer - Conclusion: don't install guzzlehttp/guzzle 7.3.0 (conflict analysis result) - Conclusion: don't install guzzlehttp/guzzle 7.4.0 (conflict analysis result) - Conclusion: don't install guzzlehttp/guzzle 7.4.4 (conflict analysis result) - Conclusion: don't install guzzlehttp/guzzle 7.5.0 (conflict analysis result) - Conclusion: don't install guzzlehttp/guzzle 7.6.1 (conflict analysis result) - Conclusion: don't install guzzlehttp/guzzle 7.7.1 (conflict analysis result) - Conclusion: don't install guzzlehttp/guzzle 7.8.0 (conflict analysis result) - Root composer.json requires php-http/guzzle7-adapter ^1.0 -> satisfiable by php-http/guzzle7-adapter[1.0.0]. - Root composer.json requires php-http/guzzle6-adapter * -> satisfiable by php-http/guzzle6-adapter[v0.1.0, ..., v0.4.1, v1.0.0, v1.1.0, v1.1.1, v2.0.0, v2.0.1, v2.0.2]. - php-http/guzzle7-adapter 1.0.0 requires guzzlehttp/guzzle ^7.0 -> satisfiable by guzzlehttp/guzzle[7.0.0, ..., 7.8.0]. - You can only install one version of a package, so only one of these can be installed: guzzlehttp/guzzle[6.0.0, ..., 6.5.8, 7.0.0, ..., 7.8.0]. - Conclusion: install guzzlehttp/guzzle 6.0.1 (conflict analysis result)