Regex to match everything except undefined XML entitites

XML, unlike HTML, only knows four named entities: <, >, ' and ".

I have been using XMLWriter in PHP to write lots of data to an XML file, and first I escape the desired text, which gives me some other entities, such as Â and ¤.

I have tried the following regex:

&(?!(apos|quot|[gl]t|amp);)

but it only matches the & and not Â or &current;. What am I doing wrong?