how to use umask() ???

Hi NG. I'm having problems with my web application changing file permissions when creating, editing or deleting text files. My web host thinks it's because I need to use umask() but I'm not quite sure just how to use this function. I've read the describtion on www.php.net but that didn't enlighten me much. (As in, don't give me a link to www.php.net because it wont help me) Can anyone explain to me how to use this function? My php application creates, reads, wrrites, copies and deletes text files and I want the file permissions to stay intact. The application needs all permissions to the files: read, write and execute (as i recall them stated when accessing through FTP). Any help would be much apreciated thanks... /Aidal