A duplicate ULID that wasn't a collision

Imagine I have this trait that gives any model a ULID-based public_id on create:

trait HasPublicId
{
  protected static function bootHasPublicId(): void
  {
    self::creating(function (self $model): void {
      if (empty($model->public_id)) {
        $model->public_id = (string) Str::ulid();
      }
    });
  }
}

Eloquent picks up the bootHasPublicId method automatically when the trait is added to a model, which is what registers the creating hook.

The empty() check lets us pass in a specific public_id from tests or an admin tool when we need a known value.

One day the app threw a database error about a duplicate public_id. ULID collisions seem impossible, so I shrugged it off as a one in a billion issue and moved on.

The next day it happened again. Different model, different customer. Ok, so something else is up.

I tracked it down to a “duplicate this record” action in the code somewhere:

public function duplicate(Order $order): RedirectResponse
{
  $copy = $order->replicate();
  $copy->save();

  return redirect()->route('orders.edit', $copy);
}

replicate() copies every attribute except the primary key, timestamps, and any columns you explicitly exclude. public_id comes along for the ride, the creating hook sees it’s not empty, and the clone saves with the original’s ULID, causing the collision.

The fix is a replicating hook:

self::replicating(function (self $model): void {
  $model->public_id = (string) Str::ulid();
});

No empty() check here on purpose. The whole point of replicating is to break the link with the source, so we always overwrite it. No more collisions!