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 :

    <?php
    
    $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.