The Response content must be a string or object implementing __toString(), "boolean" given after move to psql

Your response must return some sort of Response object. You can't just return an object.

So change it to something like:

return Response::json($promotion);

or my favorite using the helper function:

return response()->json($promotion);

If returning a response doesn't work it may be some sort of encoding issue. See this article: The Response content must be a string or object implementing __toString(), \"boolean\" given."

TL;DR

Just returning response()->json($promotion) won't solve the issue in this question. $promotion is an Eloquent object, which Laravel will automatically json_encode for the response. The json encoding is failing because of the img property, which is a PHP stream resource, and cannot be encoded.

Details

Whatever you return from your controller, Laravel is going to attempt to convert to a string. When you return an object, the object's __toString() magic method will be invoked to make the conversion.

Therefore, when you just return $promotion from your controller action, Laravel is going to call __toString() on it to convert it to a string to display.

On the Model, __toString() calls toJson(), which returns the result of json_encode. Therefore, json_encode is returning false, meaning it is running into an error.

Your dd shows that your img attribute is a stream resource. json_encode cannot encode a resource, so this is probably causing the failure. You should add your img attribute to the $hidden property to remove it from the json_encode.

class Promotion extends Model
{
    protected $hidden = ['img'];

    // rest of class
}

I got this issue when I used an ajax call to retrieve data from the database. When the controller returned the array it converted it to a boolean. The problem was that I had "invalid characters" like ú (u with accent).