Wow! I'm totally astonished to see such a patronizing article towards PHP developers on one of the biggest PHP sites. Self criticism is important, but in this article it is far beyond the truth!
The question in't "Is PHP ready for Enterprise Solutions?" but rather "Is Microsoft ready for PHP?"
Software Engineers have been trying to get the best out of both worlds (PHP & MS products) for the longest time and now Microsoft all the sudden wants to make their plattform more compatible to work with PHP. I agree, that it is a good thing! I personally look forward to a smoother composition.
However, spreading the view, that PHP professionals are likely of not being able to create enterprise solutions is ridiculous. Where do guys get that from? Is it empirical from someone who suddenly gets some extra cash from Microsoft or is looking for the personal fame?
If we're talking about experience, then let me elaborate on mine. I have been working in the IT industry for over 10 years as an IT Consultant and Software Engineer now and have met Software Engineers with various backgrounds. There are certainly differences between a MS engineers and open source engineers, but if you want to talk about flexibility, then I can assure you that an open source engineer is more likely to be able to work in the MS environment then vice versa. Again, this is just my experience. I'm not saying, that an open source developer is the better developer, but if you want to have an IT Agency create a tailored made solution that will fit perfectly into a heterogenous enterprise IT infrastrcuture (be it for SME or large enterprises), then you're not going to look for an MS Vendor.
As for the salaries go, I also feel like this is a distorted personal view! I have been part of hiring process in both US and Europe and I can tell you, that in both cases we needed to budget for more cash while bringing in PHP professionals rather than MS professionals.