apache, php, xml, and fwrite

Hi, I am still quite new to these things, and any advices are welcome. I have two question. The question 1 is after I installed zlib-1.2.1, libiconv-1.9.1, libxml2-2.5.11, libxslt-1.0.33, expat-1.95.8, php-5.0.0, and apache 1.3.31 (which load php module dynamicly). I am using OpenBSD 3.5. Everything seems correct, until I made a fwrite() call, which returns 0 indicating 0 bytes are written! The file was open by fopen(..., "w"), and is_writable() confirms it was writable. Surprising! Actually, the file can be correctly written if I disabled the xml in php by setting the option --disable-libxml when I compiled it. It seems the xml library did something driving the fwrite() crazy. The same thing was reproduced on another computer running OpenBSD 3.5 The question 2 is that the files and directories created by fopen() belong to the user "nobody" and the group "wheel". (The httpd process is owned by the user "nobody"; "wheel" is the group of "root".) But the user "nobody" is ONLY in the group "nobody". How can the files/directories created by fopen() belong to the group "wheel"? They should have the group-ship of "nobody" as well. I didn't any configuration to httpd.conf and php.ini, besides adding the php type to httpd.conf. PLEASE HELP, I cannot proceed if fwrite() doesn't do its job when xml is enabled. Thanks.