behaviors\TimestampBehavior $value

The value that will be assigned to the current attributes. This can be an anonymous function, callable in array format (e.g. [$this, 'methodName']), an \yii\behaviors\Expression object representing a DB expression (e.g. new Expression('NOW()')), scalar, string or an arbitrary value. If the former, the return value of the function will be assigned to the attributes. The signature of the function should be as follows,

function ($event)
{
    // return value will be assigned to the attribute
}

The value that will be assigned to the current attributes. This can be an anonymous function, callable in array format (e.g. [$this, 'methodName']), an \yii\behaviors\Expression object representing a DB expression (e.g. new Expression('NOW()')), scalar, string or an arbitrary value. If the former, the return value of the function will be assigned to the attributes. The signature of the function should be as follows,

function ($event)
{
    // return value will be assigned to the attribute
}

In case, when the value is null, the result of the PHP function time() will be used as value.