composer 之后的laravel没有vonder,执行一下命令即可：
laravel git:(master) ✗ composer update
Loading composer repositories with package information
Updating dependencies (including require-dev)
Package operations: 80 installs, 0 updates, 0 removals
- Installing symfony/polyfill-ctype (v1.11.0): Loading from cache
- Installing phpoption/phpoption (1.5.0): Downloading (100%)
- Installing vlucas/phpdotenv (v3.4.0): Downloading (100%)
- Installing symfony/css-selector (v4.3.2): Downloading (100%)
- Installing tijsverkoyen/css-to-inline-styles (2.2.1): Downloading (100%) - Installing symfony/polyfill-php72 (v1.11.0): Downloading (100%)
- Installing symfony/polyfill-mbstring (v1.11.0): Loading from cache
......
这个命令执行的时间比较长，很慢的，需要耐心等待一下