I\'ve built a simple form model & view, a simple AR model, and a simple controller. The form model assigns the correct values to the AR instance, but when I call save(),
In controller, change your if condition as follow :
if ($prompt = $model->post() !== null) {
This will validate that the value which is return is not null.
Your current validation condition is only validating where value is get assigned to variable $prompt or not. And that's why it's always returns true.