# I got "Declaration of ~ must be compatible with~" error in CakePHP4🍓 Cookbook

**URL:** <https://discourse.cakephp.org/t/i-got-declaration-of-must-be-compatible-with-error-in-cakephp4-cookbook/7871>\
**Category:** Need Help\
**Tags:** behavior\
**Created:** [May 27, 2020, 5:00pm UTC](https://discourse.cakephp.org/t/i-got-declaration-of-must-be-compatible-with-error-in-cakephp4-cookbook/7871 "2020-05-27T17:00:23Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![suru-yoshi](https://avatars.discourse-cdn.com/v4/letter/s/ea666f/32.png) [@suru-yoshi](https://discourse.cakephp.org/u/suru-yoshi)\
**Post date:** [May 27, 2020, 5:00pm UTC](https://discourse.cakephp.org/t/i-got-declaration-of-must-be-compatible-with-error-in-cakephp4-cookbook/7871/1 "2020-05-27T17:00:24Z")

</div>

Now I tring CMS Tutorial in CakePHP4🍓 Cookbook.  
In this part " Update Validation Rules for Articles", I made code according to the text.

```
use Cake\Validation\Validator;

```

plus

```
public function validationDefault(Validator $validator)
{
    $validator
        ->allowEmptyString('title', false)
        ->minLength('title', 10)
        ->maxLength('title', 255)

        ->allowEmptyString('body', false)
        ->minLength('body', 10);

    return $validator;

```

I made following code.

```
<?php 
namespace App\Model\Table;

use Cake\ORM\Table;
//Textクラス
use Cake\Utility\Text;

use Cake\Validation\Validator;

class ArticlesTable extends Table
{
public function initialize(array $config) : void
{
    $this->addBehavior('Timestamp');
}

public function beforeSave($event, $entity, $options)
{
    if ($entity->isNew() && !$entity->slug) {
        $sluggedTitle = Text::slug($entity->title);
        //スラグをスキーマで定義されている最大長に調整
        $entity->slug = substr($sluggedTitle, 0, 191);
    }
}

public function validationDefault(Validator $validator)
{
    $validator
        ->allowEmptyString('title', false)
        ->minLength('title', 10)
        ->maxLength('title', 255)

        ->allowEmptyString('body', false)
        ->minLength('body', 10);

    return $validator;
}

```

}

Then reload articles page. But I encountered that error.

```
Fatal error: Declaration of App\Model\Table\ArticlesTable::validationDefault(Cake\Validation\Validator $validator) must be compatible with Cake\ORM\Table::validationDefault(Cake\Validation\Validator $validator): Cake\Validation\Validator in /home/+++++/ *******.com/public_html/cms/src/Model/Table/ArticlesTable.php on line 10

```

I can’t help it.  
Someone please tell me how I solve this?  
Thank you.

---

<div class="post-metadata">

**Author:** ![Zuluru](https://yyz1.discourse-cdn.com/flex029/user_avatar/discourse.cakephp.org/zuluru/32/1230_2.png) [@Zuluru](https://discourse.cakephp.org/u/Zuluru)\
**Post date:** [May 27, 2020, 6:31pm UTC](https://discourse.cakephp.org/t/i-got-declaration-of-must-be-compatible-with-error-in-cakephp4-cookbook/7871/2 "2020-05-27T18:31:15Z")

</div>

The documentation you’ve referenced says that the function prototype is

```
public function validationDefault(Validator $validator): Validator

```

You’ve got only

```
public function validationDefault(Validator $validator)

```

Those are not exact matches.

---

<div class="post-metadata">

**Author:** ![suru-yoshi](https://avatars.discourse-cdn.com/v4/letter/s/ea666f/32.png) [@suru-yoshi](https://discourse.cakephp.org/u/suru-yoshi)\
**Post date:** [May 28, 2020, 12:04am UTC](https://discourse.cakephp.org/t/i-got-declaration-of-must-be-compatible-with-error-in-cakephp4-cookbook/7871/3 "2020-05-28T00:04:02Z")

</div>

Thank you helping.  
this problem is all of my merely misstaken.  
when I wrote,

```
public function validationDefault(Validator $validator): Validator

```

It completely worked.

In ja version document says

```
public function validationDefault(Validator $validator)

```

I suppose It’s officially wrong.

---

<div class="post-metadata">

**Author:** ![Zuluru](https://yyz1.discourse-cdn.com/flex029/user_avatar/discourse.cakephp.org/zuluru/32/1230_2.png) [@Zuluru](https://discourse.cakephp.org/u/Zuluru)\
**Post date:** [May 28, 2020, 2:55pm UTC](https://discourse.cakephp.org/t/i-got-declaration-of-must-be-compatible-with-error-in-cakephp4-cookbook/7871/4 "2020-05-28T14:55:06Z")

</div>

Yep, seems like that didn’t get updated. All the docs are in github, so you could submit a PR to correct that for others who follow.