在安装一个开源项目时，作者本地用了 PHP 7.1 进行开发，而我本地是 PHP 7.0, 于是悲剧发生了,出现了这样的错误：requires php ^7.1 -> your PHP version (7.0.13) does not satisfy that requirement..

一、Composer 安装包

composer install 之后报错

vagrant@homestead:~/Code/sample$ composer install
Loading composer repositories with package information
Installing dePEndencies (including require-dev) From lock file
Your requirements could not be resolved to an installable set of packages.

  Problem 1
    - Installation request for doctrine/instantiator 1.1.0 -> satisfiable by doctrine/instantiator[1.1.0].
    - doctrine/instantiator 1.1.0 requires php ^7.1 -> your PHP version (7.0.13) does not satisfy that requirement.
  Problem 2
    - doctrine/instantiator 1.1.0 requires php ^7.1 -> your PHP version (7.0.13) does not satisfy that requirement.
    - phpunit/phpunit-mock-objects 2.3.8 requires doctrine/instantiator ^1.0.2 -> satisfiable by doctrine/instantiator[1.1.0].
    - Installation request for phpunit/phpunit-mock-objects 2.3.8 -> satisfiable by phpunit/phpunit-mock-objects[2.3.8].

二、解决方法

删除 composer.lock 文件，重新执行 composer install，这样就能重新生成 composer.lock 文件了。

composer 包自动加载后，会生成一个 composer.lock 锁文件，所以，在从GitHub拉取别人的代码后，需要对这个文件进行删除。