Multiple replacements (WML/PHP)

Hello! I need a little bit of help on multiple replacements. I'm developing a WAP-site which will use the Swedish language (with ÅÄÖ), and I have noticed that most WML interpretors doesn't like any kind of characters outside the a-z/A-Z scope. I know that the &#<ASCII-num>; works for replacement (and that the normal HTML-way, e.g. &auml;, doesn't work). So, any suggestions on how I replace all characters in a string which are not in the normal (a-z/A-Z) scope to the &#XXX; form (e.g. 'å' -> &#228;)? best regards, johan mjones