update migration php code example

Example 1: add column in laravel migration

php artisan make:migration add_paid_to_users_table --table=users

Example 2: laravel migration rollback

To rollback one step:

php artisan migrate:rollback

To rollback multiple steps:

php artisan migrate:rollback --step=[x]
  
To drop all tables and reload all migrations:

php artisan migrate:fresh