# Writing Migrations

In order to make your package's migrations seamlessly work with the actual type, use the
`intOrBigIntBasedOnRelated()` method:

```php
class CreateProfilesTable extends Migration
{
    public function up()
    {
        Schema::create('profiles', function (Blueprint $table) {
            $table->increments('id');

            // Make `user_id` field the same type as the `id` field of the `user` table:
            $table->intOrBigIntBasedOnRelated('user_id', Schema::connection(null), 'users.id');

            //...

            $table->foreign('user_id')
                ->references('id')
                ->on('users');
        });
    }
//...
}
```

This will detect the type of `users.id`, ie. the `id` field in the `users` table and make the
`user_id` field in the `profiles` table to be the same type of field.

Internally it calls the `integer()` or the `bigInteger()` methods of the `Blueprint` class, so it's
compatible with other parts of Laravel migrations. The library also takes care of detecting whether
the field is signed or unsigned.

## Compatibility

The library was tested with:

- PHP 7.1 - 8.4
- Laravel 5.4 - 12.0
- Sqlite, MySQL (5.7, 8.0, 8.2) and Postgres (11 - 16).

## Possible Problems

~~Unfortunately~~* Doctrine DBAL cannot be properly used for detecting the existing schema with Laravel,
therefore this library is using PDO and raw engine specific queries to find out the real schema.

> *: Update Feb 2024: as Laravel 11 got rid of Doctrine DBAL now we're happy that this package just keeps working with the PDO solution 😌

As a consequence, it only works with the supported DB engines (see above).

Newer (or older) versions of the supported DB engines might return answers about their schema in a
different format than this library was prepared to. This can also lead to the impossibility of
detecting the actual field type.

To solve this problem, this package provides a configuration option where the application owner can
tell your library what the actual type of the field is.

**Next**: [Configuration »](configuration.md)