laravel eloquent json type

To define a mutator, define a setFooAttribute method on your model where Foo
  is the "studly" cased name of the column you wish to access. So, again,
lets define a mutator for the first_name attribute. This mutator will
be automatically called when we attempt to set the value of the first_name
attribute on the model:

class User extends Model
{
    public function setFirstNameAttribute($value)
    {
        $this->attributes['first_name'] = strtolower($value);
    }
}

<?php
//Array & JSON Casting
namespace App;

use Illuminate\Database\Eloquent\Model;

class User extends Model
{
    /**
     * The attributes that should be cast.
     *
     * @var array
     */
    protected $casts = [
        'options' => 'array',
    ];
}
namespace App;

use Illuminate\Database\Eloquent\Model;

class User extends Model
{
    /**
     * The attributes that should be cast.
     *
     * @var array
     */
    protected $casts = [
        'options' => 'array',
    ];
}

protected $casts = [
    'birthday' => 'date:Y-m-d',
    'joined_at' => 'datetime:Y-m-d H:00',
];