I found similar question here
but link given there is broken and that answer don't describe about IMAP IDLE in zend.
and ticket here http://zendframework.com/issues/browse/ZF-11216
Does PHP ZEND support IDLE or not ?
Zend Framework supports issuing the "NOOP" - No operation - command to the IMAP servers to renew the connection.
According to http://www.isode.com/whitepapers/imap-idle.html, this resembles the IMAP IDLE process.
Reference: Imap IDLE in Zend Framework