N°8851 N°8854 - PHP 8.4: Fix explicit nullable in functions parameters + replace trigger_error() usage with E_USER_ERROR

[Lenaick]

Base information

Question	Answer
Related to a SourceForge thread / Another PR / Combodo ticket?	8851 and 8854
Type of change?	Enhancement

Objective

To support migration to PHP8.4, we must address the new deprecation rules.
After the initial analysis, the newly deprecated features affecting iTop are :

• Implicitly nullable parameter
• Using trigger_error() with E_USER_ERROR

Proposed solution

• For "Implicitly nullable parameter" : prefix the type name with a question mark, e.g. ?CMDBObject $oObject = null
• For "trigger_error() with E_USER_ERROR": change to use E_USER_WARNING

Checklist before requesting a review

• I have performed a self-review of my code
• I have tested all changes I made on an iTop instance
• I have added a unit test, otherwise I have explained why I couldn't
• Is the PR clear and detailed enough so anyone can understand digging in the code?

[Molkobain]

Adding the nullable type hint on a class that can be extended is ok, even though its child classes don't. So we don't have to worry about APIs implementations 🙌

See this 3v4l.org test which tests the following snippet:

class A
{
    public function foo(?string $text = null)
    {
        var_dump($text);
    }
}

class B extends A
{
    public function foo(string $text = null)
    {
        var_dump($text);
    }
}

$a = new A();
$a->foo('Hello');

$b = new B();
$b->foo('Hello');

The other way around works as well, see this 3v4l.org test.

[Molkobain]

Ok for merge 🙌