Upgrade Laravel To 5.5.0 From 5.4

Note: Laravel 5.5 requires PHP 7.0.0 or higher.and Upgrade Time - 1 hour

 what you need to do: just follow steps-

 Step 1: Open composer.json file in any text editor from your laravel Project. 
Step 2:  Search laravel/framework in this file (Ctrl + f)
Step 3: Change  "laravel/framework": "5.4.*",  to   "laravel/framework": "5.5.*",
Upgrade Laravel


Step 4:  Change "phpunit/phpunit": "~5.7" to "phpunit/phpunit": "~6.0"

Finally just run composer update  in your cmd and it will update all set of packages and write a new composer.lock file.