Php SQLSTATE[23000]：完整性约束冲突：1452无法添加或更新子行：外键约束失败

为什么每次提交时都会出现错误，我认为这是正确的

控制器：

public function create()
{
    $author1['tambah_author'] = \DB::table('authors')->lists('username','id');
    $author1['id_author'] = \DB::table('authors')->lists('id');

    return View::make('article.add',$author1)->with('authors',$author1);
}

视图：

{{ Form::select('author',
                array_merge(['' => 'Pilih Author'], $tambah_author),
                $id_author,
                array('class'=>'form-control')) }}

提交时会生成错误：

SQLSTATE[23000]: Integrity constraint violation: 1452 Cannot add or update a child row: a foreign key constraint fails (`laravel`.`articles`, CONSTRAINT `articles_ibfk_1` FOREIGN KEY (`author_id`) REFERENCES `authors` (`id`) ON DELETE CASCADE) (SQL: insert into `articles` (`judul`, `body`, `author_id`, `updated_at`, `created_at`) values (sadsadd, sadas, 2, 2016-07-01 12:44:54, 2016-07-01 12:44:54))

---

您可以进行检查以确保存在有效的通讯作者

public function store() { 
    $article = new Article(); 
    $article->judul = Input::get('judul'); 
    $article->body = Input::get('isi'); 
    $article->author_id = Author::find(Input::get('author'))->id;
    if (!$article->author_id) throw new Exception('not a valid author.');
    $article->save(); 
    return Redirect::to('article'); 
}

---

您可以进行检查以确保存在有效的通讯作者

public function store() { 
    $article = new Article(); 
    $article->judul = Input::get('judul'); 
    $article->body = Input::get('isi'); 
    $article->author_id = Author::find(Input::get('author'))->id;
    if (!$article->author_id) throw new Exception('not a valid author.');
    $article->save(); 
    return Redirect::to('article'); 
}

---

有id为2的作者吗？插入DB的代码在哪里？公共函数store（）{$article=new article（）；$article->judul=Input:：get（'judul'）；$article->body=Input:：get（'isi'）；$article->author\u id=Input:：get（'author'）；$article->save（）；return Redirect:：to（'article'）；}有id为2的作者吗？插入DB的代码在哪里？公共函数store（）{$article=new article（）；$article->judul=Input:：get（'judul'）；$article->body=Input:：get（'isi'）；$article->author\u id=Input:：get（'author'）；$article->save（）；return Redirect:：to（'article'）；}无法，错误：试图获取非objecton

$article->author\u id=author:：find（Input:：get（'author'））->id的属性？相同，不能beyes，在$article->author\u id=author:：find（Input:：get（'author'））->id；无法，错误：尝试获取非objecton
$article->author\u id=author:：find（输入：：get（'author'））->id的属性？相同，不能beyes，在$article->author\u id=author:：find（Input:：get（'author'））->id；