PHP 8 migration Fatal error: Declaration must be compatible - php

Question

We are moving forward to PHP 8 from PHP 7.4, we are facing Declaration must be compatible Fatal error in our code to custom parameter type, we need a proper solution with less code changes.
Kindly refer below code snippet
ERROR
Fatal error: Declaration of ClientReactieView::getUrlAddData(?ClientReactie $clientReactie = null) must be compatible with Overview\BaseView::getUrlAddData(?Storm\Model $model = null) in /var/www/html/system/tmp/class_client_reactie_view.php on line 102
abstract class file : abstract_class_base_view.php
<?php
namespace Overview;
use Storm;
abstract class BaseView {
public static function getUrlAddData(Storm\Model $model = null){
// ...
return $urlAddData;
}
}
Child class file : class_client_reactie_view.php
<?php
class ClientReactieView extends Overview\BaseView {
public static function getUrlAddData(ClientReactie $clientReactie = null){
// ...
return $urlAddData;
}
}
Custom parameter type class_client_reactie.php
class ClientReactie extends Storm\Model {
// ...
}
Our application is already developed & working fine with PHP 7.4, We require solution to resolve this fatal error with less code changes

Answer 1

The error is telling your code is illogical.
The definition of BaseView makes a promise: you can call getUrlAddData and pass any instance of Storm\Model, or null.
The definition of ClientReactieView says that it extends BaseView, so inherits that promise. But then it changes that promise: you can call getUrlAddData, but you're not allowed to pass anything that's not a ClientReactie.
This is "covariance of input", and has always been forbidden for non-static methods - if $foo instanceof BaseView is true, then $foo->getUrlAddData(...) would have to accept all values that the definition in BaseView allowed.
What's new in PHP 8 is that this is enforced for static methods as well, so that the same guarantee applies to "late static binding" calls such as this:
abstract class BaseView {
public static function getUrlAddData(Storm\Model $model = null){
// ...
return $urlAddData;
}
public static function doSomethingElse(Storm\Model $model = null){
$urlAddData = static::getUrlAddData($model);
// ...
}
}
class ClientReactieView extends Overview\BaseView {
public static function getUrlAddData(ClientReactie $clientReactie = null){
// ...
return $urlAddData;
}
}
ClientReactieView::doSomethingElse(new Storm\Model);
// ERROR! The call goes to BaseView::doSomethingElse, which accepts any Model
// But static::getUrlAddData resolves to ClientReactieView::getUrlAddData
// and that has an incompatible signature
So the correct fix is to honour the promise made by the parent class:
class ClientReactieView extends Overview\BaseView {
public static function getUrlAddData(Storm\Model $model = null){
if ( ! $model instanceof ClientReactie ) {
// Figure out what to do with such calls
}
// ...
return $urlAddData;
}
}