how to access foriegn key in laravel database migration code example

Example 1: laravel foreign key

Schema::table('posts', function (Blueprint $table) {
    $table->unsignedBigInteger('user_id');

    $table->foreign('user_id')->references('id')->on('users');
});
OR
Schema::table('posts', function (Blueprint $table) {
    $table->foreignId('user_id')->constrained();
});

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