Your requirements could not be resolved to an installable set of packages. Problem 1 - php-http/guzzle6-adapter[v2.0.0, ..., v2.0.2] require guzzlehttp/guzzle ^6.0 -> satisfiable by guzzlehttp/guzzle[6.0.0, ..., 6.5.8]. - php-http/guzzle6-adapter v0.1.0 requires php-http/adapter ^0.1 -> satisfiable by php-http/adapter[v0.1.0]. - php-http/guzzle6-adapter[v0.4.0, ..., v0.4.1, v1.0.0, ..., v1.1.1] require php-http/httplug ^1.0 -> satisfiable by php-http/httplug[v1.0.0, v1.1.0]. - guzzlehttp/guzzle 6.5.8 requires guzzlehttp/psr7 ^1.9 -> satisfiable by guzzlehttp/psr7[1.9.0, 1.9.1]. - guzzlehttp/guzzle[6.4.0, ..., 6.5.7] require guzzlehttp/psr7 ^1.6.1 -> satisfiable by guzzlehttp/psr7[1.6.1, ..., 1.9.1]. - guzzlehttp/guzzle[6.2.3, ..., 6.3.3] require guzzlehttp/psr7 ^1.4 -> satisfiable by guzzlehttp/psr7[1.4.0, ..., 1.9.1]. - guzzlehttp/guzzle[6.2.1, ..., 6.2.2] require guzzlehttp/psr7 ^1.3.1 -> satisfiable by guzzlehttp/psr7[1.3.1, ..., 1.9.1]. - guzzlehttp/guzzle[6.0.2, ..., 6.2.0] require guzzlehttp/psr7 ~1.1 -> satisfiable by guzzlehttp/psr7[1.1.0, ..., 1.9.1]. - guzzlehttp/guzzle[6.0.0, ..., 6.0.1] require guzzlehttp/psr7 ^1.0.0 -> satisfiable by guzzlehttp/psr7[1.0.0, ..., 1.9.1]. - php-http/adapter v0.1.0 requires psr/http-message ~1.0 -> found psr/http-message[1.0, 1.0.1, 1.1] but the package is fixed to 2.0 (lock file version) by a partial update and that version does not match. Make sure you list it as an argument for the update command. - guzzlehttp/psr7[1.0.0, ..., 1.9.1] require psr/http-message ~1.0 -> found psr/http-message[1.0, 1.0.1, 1.1] but the package is fixed to 2.0 (lock file version) by a partial update and that version does not match. Make sure you list it as an argument for the update command. - php-http/guzzle6-adapter v0.2.0 requires php-http/httplug 1.0.0-alpha3 -> found php-http/httplug[v1.0.0-alpha3] but it does not match your minimum-stability. - php-http/guzzle6-adapter[v0.2.1, ..., v0.3.1] require php-http/httplug 1.0.0-beta -> found php-http/httplug[v1.0.0-beta] but it does not match your minimum-stability. - php-http/httplug[v1.0.0, ..., v1.1.0] require psr/http-message ^1.0 -> found psr/http-message[1.0, 1.0.1, 1.1] but the package is fixed to 2.0 (lock file version) by a partial update and that version does not match. Make sure you list it as an argument for the update command. - 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]. Use the option --with-all-dependencies (-W) to allow upgrades, downgrades and removals for packages currently locked to specific versions.