Improve namespace and class replacer logic

[coenjacobs]

As per @schlessera's recommendations while I was working on the classmap logic, I'm going to list some scenarios where classes or namespaces aren't properly detected that I haven't been able to fix in #4 yet here, or weren't relevant to that logic.

Class in string: $class = 'MyClass'; $obj = new $class();

It will also probably break when using relative namespaces:

namespace Vendor;
throw new Exception\MyException(); // FQCN: \Vendor\Exception\MyException

I'm not really sure how you can add cases like these without getting false positives as well, though. I don't think this can properly be handled by regexes, you should look into using nikic/PHP-Parser perhaps.

I want to get basic classmap support out the way and use this issue to list all cases where we know the logic fails and work on continually improving the replacement logic.

[Seldaek]

Hey, have you considered re-using/contributing to https://github.com/humbug/php-scoper? Seems like you're solving the same kind of problem, at least on the surface, I haven't looked in details.

[coenjacobs]

Thanks @Seldaek, I've come across that repository, but unfortunately it's not all dependency conflicts with namespaces that we're trying to solve here. The WordPress ecosystem heavily relies on global classes still (mind you, it's still PHP 5.2 compatible...) and even though there are perfectly fine solutions available to enforce a minimum PHP version for your own plugins, I want to offer a solution that works for everything right now.

[Seldaek]

Ok I see, just thought you should be aware of it but if it doesn't fit the bill that's fine :)

[coenjacobs]

I believe this is now properly addressed by #39. Will use the 0.6.0 beta 1 to test this and if needed, raise separate more specific issues.