test/app/Http/Models/PrPlan.php

<?php

namespace App\Http\Models;

use Illuminate\Database\Eloquent\Model;

class PrPlan extends Model
{
    protected $primaryKey = 'id';
    protected $table = 'pr_plan';
    public $guarded = [];
    public $casts = [
        'content_list' => 'array'
    ];
}