How do I transform "é" to é in php?

Question

I have an XML ISO-8859-1 page, in which I have to output symbols like é.
If I output é it errors out. é works just fine.
So, what PHP function should I use to transform é to é

I can't move to utf-8 (as I assume some will suggest and rightfully so) This is a huge, legacy code.

Answer 1

Use mb_convert_encoding:

mb_convert_encoding("é", "HTML-ENTITIES", "ISO-8859-1");

gives ‚.

This example does not require that you enter the "é", which you may or may not be doing in ISO-8859-1:

mb_convert_encoding(chr(130), "HTML-ENTITIES", "ISO-8859-1");