[PHP] Reserved words must not be used as class name

### Apache NetBeans version

Apache NetBeans 16

### What happened

```never```, ```mixed```, and may be other reserved words, still can be used as class name.

### How to reproduce

```php
// these statements MUST display error message.
class never {};
class mixed {};

// --- OR: ------------------------------
namespace {
class never {}
class mixed {}
}
```

### Did this work correctly in an earlier version?

No / Don't know

### Operating System

Windows 10

### JDK

Java: 14.0.1; Java HotSpot(TM) 64-Bit Server VM 14.0.1+7 Runtime: Java(TM) SE Runtime Environment 14.0.1+7

### Apache NetBeans packaging

Apache NetBeans provided installer

### Anything else

_No response_

### Are you willing to submit a pull request?

No

### Code of Conduct

Yes

Start by reproducing the PHP editor or parser behavior with the `never` and `mixed` class declarations shown in the issue. Trace the validation entry point for class names and add coverage for both declarations; done means each is reported as an error, including inside the shown namespace form.

Written by the indexing model from the issue text.