Create an appointment in Zimbra calendar using IMAP PHP library

I would like to create an appointment in my Zimbra calendar using IMAP. The final goal would be to create a cron job that doing it recurrently but for the moment I only managed to connect to the server and now I’m stuck here :

    $server_host = '{zimbra:7143/imap/novalidate-cert}';
    $server_username = '[email protected]';
    $server_password = 'mypassword';
    $imap = imap_open($server_host, $server_username, $server_password);
    if ($imap) 
        //create an appointment


I’ve searched through the whole internet there is no IMAP function in PHP to do that, I’ve only found out some Zimbra API on git which could do this but I need to use IMAP.