Yii2 - mysql default blank string displays as two single quotes in form field

I got table in MySQL with default blank string value. In SQL it looks like:

`key` TINYTEXT NOT NULL DEFAULT '',

In the model i set rule with blank string as default value:

[['key'], 'default', 'value' => ''],

And i try to do simple form with it

    <?= $form->field($model, 'key')->textarea(['rows' => 6]) ?>

In the form i see textarea with two single quotes as default value.

All fields with default blank string value got this bug.

My connection params:

return [
    'class' => 'yii\db\Connection',
    'dsn' => 'mysql:host=localhost;dbname=xxx',
    'username' => 'xxx',
    'password' => 'xxx',
    'charset' => 'utf8',
];

How can i fix it?

I try to dump $model->key before form display and got this value - two single quotes. I seen ActiveRecord::loadDefaultValues and tried dump there - got this bug there.

I found only one decision - set no default value and set blank string in the model code. But this is no right because i got other soft works with this db and it use default values.

in your model use virtual attribute, replace validation rule and form field with it

public function getKeyAttr()
{
    return $this->key == "''" ? null : $this->key;
}

public function setKeyAttr($val)
{
    $this->key = $val ? $val : "''";
}

//in rules():
[['keyAttr'], 'default', 'value' => null]

//in view:
$form->field($model, 'keyAttr')->textarea(['rows' => 6])