下面由composer使用教程欄目給大家介紹composer常見錯誤解決方法，希望對需要的朋友有所幫助！
執行composer install遇到錯誤：Your requirements could not be resolved to an installable set of packages. 這是因為不匹配composer.json要求的版本。
完整錯誤如下：
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].
提示我的PHP 7版本太高，不符合composer.json需要的版本，但是在PHP 7下應該也是可以運行的，composer可以設置忽略版本匹配，命令是：
composerinstall?--ignore-platform-reqs or composerupdate?--ignore-platform-reqs
再次執行composer命令可以正常安裝包了。
如果提示警告：
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
這是在虛擬機中執行composer，提示這個目錄沒有可寫權限，composer無法緩存下載的包，這樣就每次都得重新下載，把目錄改成可寫可讀即可。
sudo?chmod?-R?777?/home/vagrant/.composer/cache/files/
另外，在虛擬機中也設置composer為國內鏡像，不然下載速度慢的要死，執行：
composerconfig?-g?repo.packagistcomposerhttps://packagist.phpcomposer.com
OK，大功告成。
更多composer相關技術文章，請訪問composer欄目：composer
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