1. Is PHP5 production ready ?
No, not yet. I have been "playing" with it on some development machine I have here, not seen any real show stoppers but I am always nervous about putting a new release on any production machines.
2. Does PHP5 deliver better performance than C++ in CGI env ?
That depends on yours apps, you can get a few performance tools from zend. The best way to look at this would be use some benchmarking tools and see what it's like. PHP 5 has some nice XML stuff that *should* be pretty close to C++. But at the end of the day if the PHP version is 5% slower, surely the development savings will enable you to get better hardware :-)
3. Are the new 'oo' language constructs stable enough to go in
with a major 200,000 line project re-write for a application
portal ?
The applications I have been testing it on are not far behind the 200K lines and I have had no major issues. Alot of it needs to be redone as it's written in PHP4, to take advantage of the new features but from we have seen so far it's all good.
4. the XML+XSLT transforms will be achieved through 'exec 'xsltproc approach. The average XML file size is 125KB. Is there a better way to handle this situation ?
Can you do any caching?
5. How has been the experience with some of the experienced folks on this list who have used it for transaction heavy environments ?
The systems I use it on process SMS messages that send out mobile content. Most of the Networks use XML, a typical application can easily process hundreds of these transactions per second. I use PHP in a command line envoirment as well as web. The development time is key in my envoirment.
Outsourcing is another headache that I have to handle, and I am quite
jittery with that as well.
Good luck on that one mate !. :-) why not retrain the C++ developers?