get（）不起作用，但是First（）起作用。 我需要使用get（）获取所有数据

Question

I have a page that shows categories/main posts which when clicked will navigate to a page with sub-posts concerning the topic of the main post. The problem is, however, that when I try to use ->get() It shows the following error:

The function I use to get the information is the following (URL Shows as slug):

public function knowledge_collection($slug, Request $request){
    $knowledge_post_primary = Knowledge::where('knowledge_slug', $slug)->get();
    //dd($knowledge_post_primary);
    $knowledge_posts = Knowledge_Post::where('parent_id', $knowledge_post_primary->id)->get();
    return view('knowledge.knowledge_posts', compact('knowledge_posts', 'knowledge_post_primary'));
}

It's most likely an easy fix, but I can't seem to find it. I hope someone else can and will be able to help me :)

I've tried requesting the data in different ways and with a FindorFail(), but nothing worked up till now.

EDIT: The screenshot that was asked for.

EDIT EDIT: After using @Gulshans code I got the following error:

Answer 1

Try this for single result:

$knowledge_post_primary = Knowledge::where('knowledge_slug','=',$slug)->first()->toArray();
if(!empty($knowledge_post_primary)){
   $knowledge_posts = Knowledge_Post::where('parent_id', '=',$knowledge_post_primary['id'])->get();
}

Try this for multiple result:

 $knowledge_post_primary = Knowledge::where('knowledge_slug','=',$slug)->get()->toArray();
 if(!empty($knowledge_post_primary)){
       foreach($knowledge_post_primary as $post_primary){
       $knowledge_posts = Knowledge_Post::where('parent_id', '=',$post_primary['id'])->get()->toArray();
          dd($knowledge_posts);
       }
  }

Answer 2

If you want to get Knowledge_Post for the knowledge_slug and if there is only one Knowledge record you should use

public function knowledge_collection($slug, Request $request){
    $knowledge_post_primary = Knowledge::where('knowledge_slug', $slug)->first();
    $knowledge_posts = Knowledge_Post::where('parent_id', $knowledge_post_primary->id)->get();
    return view('knowledge.knowledge_posts', compact('knowledge_posts', 'knowledge_post_primary'));
}

if there is many records and want Knowledge_Posts related to all it will be whereIn, to get all ids, you should use pluck('id')->all() or pluck('id')->toArray()

public function knowledge_collection($slug, Request $request){
        $knowledge_post_primary_Ids = Knowledge::where('knowledge_slug', $slug)->pluck('id')->all();
        $knowledge_posts = Knowledge_Post::whereIn('parent_id', $knowledge_post_primary_Ids)->get();
        return view('knowledge.knowledge_posts', compact('knowledge_posts', 'knowledge_post_primary'));
    }