How can I add field using alter table on the migration laravel?

I use laravel 5.3

My migration like this :

<?php
use Illuminate\Support\Facades\Schema;
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Database\Migrations\Migration;
class CreateUsersTable extends Migration
{
    public function up()
    {
        Schema::create('users', function (Blueprint $table) {
            $table->increments('id');
            $table->string('name');
            $table->string('api_token')->nullable();
            $table->string('email',100)->unique();
            $table->string('password')->nullable();
            $table->string('avatar',100)->nullable();
            $table->string('full_name',100)->nullable();
            $table->date('birth_date')->nullable();
            $table->smallInteger('gender')->nullable();
            $table->timestamps();
            $table->softDeletes();
        });
    }
    public function down()
    {
        DB::statement('SET FOREIGN_KEY_CHECKS = 0');
        Schema::dropIfExists('users');
        DB::statement('SET FOREIGN_KEY_CHECKS = 1');
    }     
}

I want to add new field like this :

$table->string('mobile_number',20)->nullable();

But I don't want to add it on the schema. I want to use alter table

On my staging server and live server had set automatic migration

So if I use alter table, it will automatic migration. So on the table in database will automatic add mobile_number field if the code merge to development or master

If I add on the schema, it will not automatically migrate

How can I add the field using alter table?

via Chebli Mohamed