html_entity_decode problem with gb2312 charset and numeric entities

Hello.

I try to use the html_entity_decode function to pass from numeric HTML 
character codes to the gb2312 charset.
example: I want the string "供桌面" be converted in it's 
gb2312 charset, someting like: "¹©×ÀÃæʹÓõÄ×ÔÈ".
Is there a way to do this ? I tried already the numeric conversion code from 
daniel at brightbyte on this page:
http://ch2.php.net/html_entity_decode
But without any success, because chr() can only convert values until 255.

Shouldn't html_entity_decode() perform this kind of numeric conversions for 
all charsets defined in that function ? (maybe a feature request)

Thank you for any help.
Daniel