To enable Cyrus IMAP support and to use these functions you have to compile
PHP with the --with-cyrus option.
Warning
The IMAP extension cannot be used in conjuction with
the recode, YAZ or Cyrus extensions. This is due to the fact that they
both share the same internal symbol.
The constants below are defined by this extension, and
will only be available when the extension has either
been compiled into PHP or dynamically loaded at runtime.