일반적인 Composer 오류 및 해결 방법

vagrant@homestead:/usr/share/nginx/html/laravel-blog$ sudocomposerinstall
Loadingcomposerrepositorieswithpackage information
Installingdependencies (includingrequire-dev) fromlockfile
Yourrequirementscouldnot beresolvedto aninstallablesetofpackages.
  
  Problem 1
    - Installationrequestfor doctrine/instantiator 1.0.3 -> satisfiablebydoctrine/instantiator[1.0.3].
    - doctrine/instantiator 1.0.3 requiresphp ~5.3 -> yourPHPversion (7.0.3) doesnot satisfythatrequirement.
  Problem 2
    - doctrine/instantiator 1.0.3 requiresphp ~5.3 -> yourPHPversion (7.0.3) doesnot satisfythatrequirement.
    - phpunit/phpunit-mock-objects 2.3.0 requiresdoctrine/instantiator ~1.0,>=1.0.1 -> satisfiablebydoctrine/instantiator[1.0.3].
    - Installationrequestfor phpunit/phpunit-mock-objects 2.3.0 -> satisfiablebyphpunit/phpunit-mock-objects[2.3.0].

composerinstall --ignore-platform-reqs

composerupdate --ignore-platform-reqs

Cannotcreatecachedirectory /home/vagrant/.composer/cache/repo/https---packagist.org/, or directoryis not writable. Proceedingwithoutcache
  Cannotcreatecachedirectory /home/vagrant/.composer/cache/files/, or directoryis not writable. Proceedingwithoutcache

sudo chmod -R 777 /home/vagrant/.composer/cache/files/

composerconfig -g repo.packagistcomposerhttps://packagist.phpcomposer.com