Laravel Factory: Manual Increment of Column

To achieve true autoIncrement rather use this approach:

   $__count = App\AliasCommand::count();
   $__lastid = $__count ? App\AliasCommand::orderBy('order', 'desc')->first()->id : 0 ;


   $factory->define(App\AliasCommand::class,
       function(Faker\Generator $faker) use($__lastid){

       return [

         'user_id' => App\User::inRandomOrder()->first()->id,
         'command' => $faker->word,
         'content' => $faker->sentence,
         'order'   => $faker->unique()->numberBetween($min=$__lastid+1, $max=$__lastid+25),

         /*  +25 (for example here) is the number of records you want to insert 
             per run.
             You can set this value in a config file and get it from there
             for both Seeder and Factory ( i.e here ).
         */
      ];

   });

The answer by @apokryfos is a good solution if you're sure the factory model generations will only be run in sequential order and you're not concerned with pre-existing data.

However, this can result in incorrect order values if, for example, you want to generate models to be inserted into your test database, where some records already exist.

Using a closure for the column value, we can better automate the sequential order.

$factory->define(App\AliasCommand::class, function (Faker\Generator $faker) {
    return [
        'user_id' => App\User::inRandomOrder()->first()->id,
        'command' => $faker->word,
        'content' => $faker->sentence,
        'order'   => function() {
            $max = App\AliasCommand::max('order'); // returns 0 if no records exist.

            return $max+1;
        }
    ];
});

You almost had it right in your example, the problem is that you were running the order value execution at the time of defining the factory rather than the above code, which executes at the time the individual model is generated.

By the same principle, you should also enclose the user_id code in a closure, otherwise all of your factory generated models will have the same user ID.

Here's something that might work.

$factory->define(App\AliasCommand::class, function (Faker\Generator $faker) {
    static $order = 1;   
    return [
        'user_id' => App\User::inRandomOrder()->first()->id,
        'command' => $faker->word,
        'content' => $faker->sentence,
        'order'   => $order++
    ];
});

It just keeps a counter internal to that function.

Update:

Laravel 8 introduced new factory classes so this request becomes:

class AliasCommandFactory extends Factory {

    private static $order = 1;

    protected $model = AliasCommand::class;

    public function definition() {
         $faker = $this->faker;
         return [
            'user_id' => User::inRandomOrder()->first()->id,
            'command' => $faker->word,
            'content' => $faker->sentence,
            'order'   => self::$order++
        ];
    }
}