我从作曲家那里得到的错误信息是:您的要求无法解析为可安装的一组包.
Problem 1
- Installation request for laravel/framework v5.4.28 -> satisfiable by laravel/framework[v5.4.28].
- laravel/framework v5.4.28 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
Problem 2
- Installation request for phpunit/phpunit 5.7.21 -> satisfiable by phpunit/phpunit[5.7.21].
- phpunit/phpunit 5.7.21 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
Problem 3
- laravel/framework v5.4.28 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
- laravel/tinker …