Description
bool 
imap_ping ( resource imap_stream )
  
     Returns TRUE if the stream is still alive, FALSE otherwise.
    
     imap_ping() pings the stream to see if it's still 
     active. It may discover new mail; this is the preferred method for a 
     periodic "new mail check" as well as a "keep alive" for servers which
     have inactivity timeout.
    
     
例子 1. imap_ping() Example 
<?php
  $imap = imap_open("{your.imap.host}", "mailadmin", "password");
  // after some sleeping if (!imap_ping($imap)) {     // do some stuff to reconnect }
  ?>
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