2
If you use PHP embedded XML parser, the right way:
1 convert XML contents encoded with other charsets to one of the XMLparser valid charsets (utf8,iso-8859-1 and us-ascii)
2 parse contents
3 convert contents from the valid charset to your desired charset
There is alternative technique that does not use the embedded parser and no need the conversions. But the technique is still in an experimental stage.
You could try xmline which is used by most Chinese users for XML parsing with complex charset conversion