PHP v4.1.1 WDDX problems

Hi All, I am attempting to compiler php v4.1.1 as a fast cgi runner with WDDX. I get all the way through the compile and it get's stuck at: ./.libs/libphp4.a(wddx.o): In function `php_wddx_push_element': /usr/local/src/php-4.1.1/ext/wddx/wddx.c:780: undefined reference to `xml_utf8_decode' ./.libs/libphp4.a(wddx.o): In function `php_wddx_process_data': /usr/local/src/php-4.1.1/ext/wddx/wddx.c:911: undefined reference to `xml_utf8_decode' I take it that it's having some problems linking to the xml module? Any ideas?