After becoming somewhat estranged open source, and spending some years developing web applications in ASP.Net, I\'m going to start doing quite a lot of PHP / MySQL development.
In theory, PHP and MySQL should be completely platform-independent.
In practice, if you're going to have a real production application, I suggest you to have a testing environment mirroring the production one, to avoid surprises.
No.
VirtualBox + Shared folders should be useful if you have about 6-8 hours free on one weekend to get all VBox basics clear and settings worked out.
If you're switching to Linux, the process may take upto a month and you will be highly unproductive in that time, in terms of production code.
It is a good idea to keep practicing Linux on VBox for Windows, in advance before switching, using one of [PCLinuxOS, CentOS, OpenSuse, Ubuntu]. I prefer CentOS, PCLinuxOS.
There's a gem called SLAMPP and another beauty called XAMPP <-- works on Linux and Windows.
IMO, as a rough guesstimate, if you expect to code 2000-3000 lines of code (that you write/add) per project, for 6mo-1yr, stick to Windows and master Linux meanwhile using VBox.
If above that, or if you plan to make a cool new LAMP website, I think you should switch to Linux first. Take a month more to get used to Linux. You can still shuffle around with dual boot or VBox for as long as you like, starting as early as you can - learning Linux enough to debug a LAMP app does take time.
It's worth having a LAMP sandbox so you can get to know where to find - and how to edit - config files, get comfortable with restarting services, handling scheduled jobs etc. if you are going to have to deal with these tasks in production.
No, because pretty much the only thing you can't do on WAMP if you target LAMP is using System()/Exec Calls, and usually that is a good thing because those should be used very sparsely.
Yes I would recommend developing on an environment as close to your production environment as possible. There are differences between how PHP works on Windows as compared to Linux. And other differences like how Linux handles file permissions as compared to Windows. I run the free VMWare server with a Linux virtual machine. I have a Samba share on the Linux VM that I mount as a networked drive in Windows. Then I use Eclipse on Windows as my code editor.
No, developing on wamp and running on lamp should be fine, but at least stage on lamp. I've gone both ways without many problems (ok, there used to be a bunch of problems deploying enterprise sites on WAMP (don't try to use the PHP ISAPI filter) but they are solvable now (fastcgi)). As long as you aren't adding any PECL modules that state they aren't supported on Windows, you shouldn't have any problems. Also (since you are stating you are using WAMP I assume you are using MySql), mssql and PHP have a bunch of issues (the ancient driver it requires seriously limits the length of your query).