its so annoying to debug xampp version which can connect to oracle db in windows server 2012 r2, so this is the clue
1. download xampp 7.2 portable
https://sourceforge.net/projects/xampp/files/XAMPP%20Windows/7.2.13/
2. extract in C:\
3. download visual c redistribute 2015 download x64 & get x86 and install both 32 & 64
https://www.microsoft.com/en-us/download/details.aspx?id=52685
4. visual c redistribute 2013, download x64 & get x86 and install both 32 & 64
https://support.microsoft.com/en-us/help/3179560/update-for-visual-c-2013-and-visual-c-redistributable-package
5. download and extract instant client
https://www.oracle.com/technetwork/topics/winsoft-085727.html
6. , copy all .dll file to
c:\apache\bin
c:\php\
7. makesure c:\xampp\php\ext\php_oci8_12c.dll exists
8. Enable php extension in php.ini extension=oci8_12c
9. start apache
if the apache still cannot start, download xampp with php5 and start again from “no 2, extract to C ”
https://sourceforge.net/projects/xampp/files/XAMPP%20Windows/5.6.39/
Thanks!