Indeed it is.
Especially in a particular case I had with Apache 2.0.63 & Windows.
So, I learned:
1. You need to make sure your PHP installer has "VC6" in the name and not "VC9" (as that's for IIS servers).
2. It needs to be the thread safe version.
3. Also, I couldn't get PHP 5.3.1 to work with Apache 2.0.63 at all. No matter which dll file I used. So I downloaded the zip of 5.2.12 (php-5.2.12-Win32-VC6-x86.zip), extracted it to C:\PHP and configured: LoadModule php5_module "c:/PHP/php5apache2.dll" in my httpd.conf.
This site helped at some point too.
Then all was fine.