how to downgrade laravel version 5.8 to 5.1 in ubuntu server?

"name": "laravel/laravel", "description": "The Laravel Framework.", "keywords": [ "framework", "laravel" ], "license": "MIT", "type": "project", "require": { "php": ">=5.5.9", "laravel/framework": "^5.8.0",

via Chebli Mohamed