Function is unknown as the OCI (Oracle Call Interface), a DLL that exports that function, did not load.
Make sure that the correct directory, containing that DLL, is part of the PATH - this is used by the PHP executable process when it loads (either statically or dynamically) the OCI DLL.
Make sure that the PHP environment itself, is correct. For example, you showed PHP.INI with entry ";extension=php_oci8_12c.dll" - which means it is a comment line and not a configuration entry.
Thanks. Dislike cross postings.