Laravel 5.6项目迁移后执行php artisan serve报错求助

错误原因 #

这个报错的核心问题是项目依赖包不完整。Laravel项目的第三方依赖都存放在vendor目录下，而该目录通常不会被同步或拷贝（体积大且可通过Composer重新生成），你从朋友电脑迁移项目时，要么没拿到完整的vendor目录，要么目录内文件缺失、损坏，导致系统找不到symfony/polyfill-mbstring这个必要依赖文件，进而触发加载错误。

解决步骤 #

• 确保本地环境已安装Composer（XAMPP环境下PHP正常即可运行Composer）
• 打开命令行，切换到项目根目录：

  cd D:\xampp\htdocs\ecommerce
  

• 执行Composer命令安装依赖：

  composer install
  

  该命令会根据项目根目录的composer.lock文件，安装所有指定版本的依赖包，自动补全缺失的vendor目录内容
• 依赖安装完成后，配置环境文件：
  1. 复制项目根目录的.env.example文件，重命名为.env
  2. 执行命令生成应用密钥：

     php artisan key:generate
     

• 完成以上步骤后，再执行php artisan serve即可正常启动项目

原始报错信息 #

PS D:\xampp\htdocs\ecommerce> php artisan serve
PHP Warning:  require(D:\xampp\htdocs\ecommerce\vendor\composer/../symfony/polyfill-mbstring/bootstrap.php): Failed to open stream: No such file or directory in D:\xampp\htdocs\ecommerce\vendor\composer\autoload_real.php on line 66

Warning: require(D:\xampp\htdocs\ecommerce\vendor\composer/../symfony/polyfill-mbstring/bootstrap.php): Failed to open stream: No such file or directory in D:\xampp\htdocs\ecommerce\vendor\composer\autoload_real.php on line 66
PHP Fatal error:  Uncaught Error: Failed opening required 'D:\xampp\htdocs\ecommerce\vendor\composer/../symfony/polyfill-mbstring/bootstrap.php' (include_path='D:\xampp\php\PEAR') in D:\xampp\htdocs\ecommerce\vendor\composer\autoload_real.php:66
Stack trace:
#0 D:\xampp\htdocs\ecommerce\vendor\composer\autoload_real.php(56): composerRequire444c8f1f8d742ab877cec02cbb1b7feb('0e6d7bf4a5811bf...', 'D:\xampp\htdocs...')
#1 D:\xampp\htdocs\ecommerce\vendor\autoload.php(7): ComposerAutoloaderInit444c8f1f8d742ab877cec02cbb1b7feb::getLoader()
#2 D:\xampp\htdocs\ecommerce\artisan(18): require('D:\xampp\htdocs...')
#3 {main}
  thrown in D:\xampp\htdocs\ecommerce\vendor\composer\autoload_real.php on line 66

Fatal error: Uncaught Error: Failed opening required 'D:\xampp\htdocs\ecommerce\vendor\composer/../symfony/polyfill-mbstring/bootstrap.php' (include_path='D:\xampp\php\PEAR') in D:\xampp\htdocs\ecommerce\vendor\composer\autoload_real.php:66
Stack trace:
#0 D:\xampp\htdocs\ecommerce\vendor\composer\autoload_real.php(56): composerRequire444c8f1f8d742ab877cec02cbb1b7feb('0e6d7bf4a5811bf...', 'D:\xampp\htdocs...')
#1 D:\xampp\htdocs\ecommerce\vendor\autoload.php(7): ComposerAutoloaderInit444c8f1f8d742ab877cec02cbb1b7feb::getLoader()
#2 D:\xampp\htdocs\ecommerce\artisan(18): require('D:\xampp\htdocs...')
#3 {main}
  thrown in D:\xampp\htdocs\ecommerce\vendor\composer\autoload_real.php on line 66
PS D:\xampp\htdocs\ecommerce>

内容的提问来源于stack exchange，提问作者Semeon