It won’t work to simply download only oci.dll from some site (you can download it from several). The file oci.dll is part of the Oracle C Interface. Unless you need to use Oracle, I suggest you go to the relevant line inside the php.ini file and uncomment the loading of this extension. However, if you need to use this extension, you’ll need to install the free Oracle Client libraries and add them to the path. It is a bit more involved then that, though, but Oracle has a nice article describing how to install PHP and the Oracle Instant Client on Linux or Windows