firefly-iii/app/Models/Preference.php

<?php namespace FireflyIII\Models;

use Illuminate\Database\Eloquent\Model;

class Preference extends Model
{

    public function getDataAttribute($value)
    {
        return json_decode($value);
    }

    public function setDataAttribute($value)
    {
        $this->attributes['data'] = json_encode($value);
    }

    public function user()
    {
        return $this->belongsTo('User');
    }

}