A trait to help deal with handling empty strings in Eloquent models

example.blade.php

<p>If the $nullableDefault property is set on your model, you will see that value instead of an empty string. For example {{ $product->size }} would show N/A instead of an empty string if the value is null.</p>

<p>However, you might not want N/A to show up in a form input, so the original value (null) will be provided if you request the raw value:</p>

<form>
    <input type="text" name="size" value="{{ $product->size_raw }}">
</form>

NullableFields.php

<?php

namespace App\Models;

/**
 * Converts empty values to nulls before saving a model to storage.
 */
trait NullableFields
{
    /**
     * Boot the trait.
     *
     * @return void
     */
    public static function bootNullableFields()
    {
        // Register a callback to be triggered when the model is saving that 
        // will unset any nullable fields that are set to empty strings.
        static::saving(function ($model) {
            foreach ($model->getNullableFields() as $field) {
                if ($model->getAttribute($field) === '') {
                    unset($model->{$field});
                }
            }
        });
    }

    /**
     * Checks if the given key is replaceable.
     *
     * @param string $key
     *
     * @return boolean
     */
    public function fieldIsReplaceable($key)
    {
        // A field is not replaceable if...

        // ...the nullableDefault property has not been declared.
        if (!property_exists($this, 'nullableDefault')) {
            return false;
        }

        // ...the given key is not marked as nullable on the model.
        if (!in_array($key, $this->getNullableFields())) {
            return false;
        }

        // ...it already has a value.
        if ($this->getAttribute($key) != '') {
            return false;
        }

        // ...the user is requesting the raw value.
        if (strtolower(substr($key, -3)) == 'raw') {
            return false;
        }

        return true;
    }

    /**
     * Gets the nullable fields.
     *
     * @return array
     */
    public function getNullableFields()
    {
        return $this->nullable;
    }

    /**
     * Gets the nullable default value.
     *
     * @return string
     */
    public function getNullableDefault()
    {
        return $this->nullableDefault;
    }
    
    /**
     * Dynamically retrieve attributes on the model.
     *
     * @param string $key
     *
     * @return mixed
     */
    public function __get($key)
    {
        // Replace an empty nullable value with the nullable default.
        if ($this->fieldIsReplaceable($key)) {
            return $this->getNullableDefault();
        }

        // Let Laravel handle the call.
        return parent::__get($key);
    }
}

Product.php

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Model;

class Product extends Model
{
    use NullableFields;

    /**
     * @var array
     */
    protected $fillable = [
        'category_id',
        'name',
        'brand',
        'size',
        'sku',
        'description',
        'location',
    ];

    /**
     * @var array
     */
    protected $nullable = [
        'size',
        'location',
    ];

    /**
     * @var string
     */
    protected $nullableDefault = 'N/A';
}