phpinfo
_ENV[\"ORACLE_HOME\"] C:\\oracle\\instantclient_11_2\\
_ENV[\"OS\"] Windows_NT
_ENV[\"Path\"] C:\\WINDOWS\\system32;C:\\WINDOWS;C:\\WINDOWS\\System32
I solved it copying all the content of C:\instantclient_11_2 (please check what´s yours) inside system and system32 folders in Windows , then I delete the path of C:\instantclient_11_2 in the PATH enviroment variable.
I am using XAMPP and Windows 8 and it´s the first time I see this issue. I always configured properly oci 8 with xampp and windows in a few minutes. I hope this would help you.