...🤯

Nice shot, really!

If somebody here is wondering why this fixes the issue, and why this works as expected, here a related documentation:

.... One exception to this rule are arguments of the form Type $param = null, where the null default makes the type implicitly nullable. This usage remains allowed, though it is recommended to use an explicit nullable type instead.
— https://www.php.net/manual/en/functions.arguments.php#functions.arguments.type-declaration

Also this scarying warning deserves a note:

It is also possible to achieve nullable arguments by making null the default value. This is not recommended as if the default value is changed in a child class a type compatibility violation will be raised as the null type will need to be added to the type declaration.
— https://www.php.net/manual/en/language.types.declarations.php#language.types.declarations.nullable

So, premising we are aware of that concern, here we are vaxinated for that, since this is not a class method but a beautiful function, so the type violation thing is just nowhere a concern.

Probably in 2 years a random folk will propose an RFC to deprecate this null thing aaaand in that case we will just kill that person.

Tested also in very legacy stuff like PHP 5.1 aaaand it works.

Thaaaank🥇