To get these functions to work, you have to compile PHP with --with-imap. That requires the c-client library to be installed. Grab it from ftp://ftp.cac.washington.edu/imap/imap-4.2.tar.Z and compile it. Then copy c-client/c-client.a to /usr/local/lib or some other directory on your link path and copy c-client/rfc822.h, mail.h and linkage.h to /usr/local/include or some other directory in your include path.