php - Laravel Eloquent create returning null id

I have an Eloquent modelFoo, with a publicbar array:

class Foo extends Model
{
    public $bar = ['a', 'b', 'c'];
}
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In thestore method of my controller I want to access these variables, and create a newFoo object:

public function store(Request $request)
{
    $foo = new Foo;

    foreach ($foo->bar as $field) {
        $data[$field] = $request->{$field};
    }

    $foo->create($data);

    return $foo->id;
}
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The problem is that$foo->id isnull, although the object is created successfully.