如果提示symfony版本过高那么安装低版本的symfony即可
Problem 1
- Installation request for spatie/laravel-pjax 1.3 -> satisfiable by spatie/laravel-pjax[1.3.0].
- Conclusion: remove symfony/css-selector v4.2.4
- Conclusion: don't install symfony/css-selector v4.2.4
composer require symfony/css-selector 3.0
如果是提示laravel版本太低