ANSI is not a real encoding. It's a word that basically means "whatever encoding my Windows computer is configured to use". Getting ANSI is a clear sign of relying on default encoding somewhere.
In order to generate valid UTF-8 output, you have to feed all XML functions with proper UTF-8 input. The most straightforward way to do it is to save your PHP source code as UTF-8 and then just type some non-English letters. If you are reading data from external sources (such as a database) you need to ensure that the complete toolchain makes proper use of encodings.
Whatever, using "Save as" in an undisclosed piece of software is not a reliable way to determine the file encoding.