Laravel 尝试获取非对象的属性 'project_name'。

我对Laravel还很新，只是想指出一下。我在读取我的展示页面时遇到了问题，当我打开展示页面(show.blade.php)时，返回了以下错误：

试图获取非对象的属性'project_name'（视图：C:\Server\data\htdocs\ProjectCMS\resources\views\project\show.blade.php）。

我不知道我做错了什么，因为我已经让它起作用了，但是一旦我再次打开展示页面，就会返回这个错误。

任何帮助将不胜感激！

ProjectController.php：

public function show($id)
{
    $user_id = auth()->user()->id;
    $project = Project::where('user_id', $user_id)->first();
    $projectitem = Projectitem::where('project_id', $id)->first();
    return view('project.show', [
        'project'     => $project,
        'projectitem' => $projectitem,
    ]);
}

web.php路由

Route::get('/projects/{id}', 'ProjectController@show');

show.blade.php：

@extends('layouts.app')
@section('content')
                
{{$projectitem->project_name}}
                    
Beschrijving:
                    {!!$projectitem->description!!}
                    
Tijdsduur(in uren): {{$projectitem->time_span}} Uren
                    
Opdrachtgever:  {{$projectitem->client}}
                    
Text verslag:
                    {!!$projectitem->text_report!!}
                    
Foto's vooraf:  
                    {!!$projectitem->images_before!!}
                    
Foto's achteraf:  
                    {!!$projectitem->images_after!!}
                            
Beschikbaar op:  
                            
Facebook: facebook == 1){echo "wel";}else{echo "niet";}?>
                            
Instagram: instagram == 1){echo "wel";}else{echo "niet";}?>
                            
Linkedin: linkedin == 1){echo "wel";}else{echo "niet";}?>
                            
Website: website == 1){echo "wel";}else{echo "niet";}?>
                    
Aangemaakt door: {{$projectitem->created_by}}
                            
Aangemaakt op: {{$projectitem->created_at}}
                            
Laatst gewijzigd op: {{$projectitem->updated_at}}
@endsection

Projectitem.php（模型）

namespace App;
use Illuminate\Database\Eloquent\Model;
class Projectitem extends Model
{
    protected $table = "project_item";
    function project(){
        return $this->belongsTo('App\Project');
    }
}

Project.php（模型）

hasMany('App\Projectitem');
    }
}

migration projectitem表

 public function up()
{
    Schema::create('project_item', function (Blueprint $table) {
        $table->bigIncrements('id');
        $table->string('project_name');
        $table->string('client');
        $table->text('description');
        $table->float('time_span');
        $table->text('text_report');
        $table->text('images_before');
        $table->text('images_after');
        $table->boolean('facebook');
        $table->boolean('instagram');
        $table->boolean('linkedin');
        $table->boolean('website');
        $table->integer('belongs_to');
        $table->string('created_by');
        $table->timestamps();
    });
}