No matter the directory I put in the directive extension_dir in php.ini file, the extension is unloadable.
I receive the message: 

"Unable to load dynamic library 'c:\inetpub\php\extensions\php_oci8dll' - Cannot find specified module"
and
PHP Warning: Unable to load dynamic library 'c:\inetpub\php\extensions\php_oci8.dll' 

I've tryed many ways in php.ini file:
extension_dir = "c:\inetpub\php\extensions"
extension_dir = "c:\inetpub\php\extensions\"
extension_dir = "c:\\inetpub\\php\\extensions\\"
extension_dir = "c:\\inetpub\\php\\extensions"
extension_dir = c:\inetpub\php\extensions
extension_dir = c:\inetpub\php\extensions\
extension_dir = c:/inetpub/php/extensions/
extension_dir = c:/inetpub/php/extensions

None of these worked.