PHP itself and also modules, like mysql.dll
can be compiled ts, thread safe
or nts non-thread-safe
Now, if your php.exe is compiled or a part of a ZIP download of php-package
which was compiled TS
PHP compiled with module API=20060613, debug=0, thread-safety=1
then you can get an error if you use modules, extensions, like mysql.dll etc.
which are compiled NTS, non-thread-safe
Usually for PHP download, the file, installer or zip
which has NTS in package name is non-thread-safe.
If there is nothing about TS/NTS in the package name
it is usuallt TS. Thread safe is default, if not NTS is mentioned.
I run Apache 2.2 on Windows XP.
For this they recommend TS, PHP Package compiled thread safe.
So I installed php-5.3.0-Win32-VC6-x86 .. = thread safe
and not the alternative:
php-5.3.0-nts-Win32-VC6-x86
This means that some modules, extensions, if I download them separate afterwards
which are NTS, can eventually cause an error.
Because there is a mismatch with the way my PHP was compiled.