PHP 5.5+ require at least Windows 2008/Vista, or 2008r2, 2012, 2012r2, 2016 or 7, 8, 8.1, 10. Either 32-Bit or 64-bit (aka X86 or X64. PHP does not run on Windows RT/WOA/ARM). As of PHP 7.2.0 Windows 2008 and Vista are no longer supported.
PHP requires the Visual C runtime(CRT). Many applications require that so it may already be installed.
PHP 5.5 and 5.6 require VC CRT 11 (Visual Studio 2012). See: » https://www.microsoft.com/en-us/download/details.aspx?id=30679
PHP 7.0 and 7.1 require VC CRT 14 (Visual Studio 2015). PHP 7.2 and 7.3 require VC CRT 15 (Visual Studio 2017). PHP 7.4+ requires VC CRT 16 (Visual Studio 2019). The Microsoft Visual C++ Redistributable for Visual Studio 2019 is suitable for all these PHP versions, see » https://visualstudio.microsoft.com/downloads/.
You MUST download the x86 CRT for PHP x86 builds and the x64 CRT for PHP x64 builds.
If CRT is already installed, the installer will tell you that and not change anything.
The CRT installer supports the /quiet and /norestart command-line switches, so you can script running it.
VC11 CRT DLLs can be copied from your local machine to a remote machine(a `Copy Deployment` installation) instead of running the installer on the remote machine (such as a web server you have restricted access to).
VC14 CRT does not support a `Copy Deployment` installation. VC14 CRT has many more DLLs(most in files with names starting with api-*). If you can find them all and copy them, it will also work (try a tool like Resource Hacker to get a list of all the DLLs to copy).