(PECL zmq >= 0.5.0)
ZMQSocket::__construct — Construct a new ZMQSocket
$context
   , int $type
   [, string $persistent_id = null
   [, callback $on_new_socket = null
  ]] )
   Constructs a ZMQSocket object. persistent_id parameter can be used to allocated a persistent
   socket. A persistent socket has to be allocated from a persistent context and it stays connected over multiple requests.
   The persistent_id parameter can be used to recall the same socket over multiple requests. The     
   on_new_socket is called only when a new underlying socket structure is created.
  
contextZMQContext object.
type
       The socket type. See ZMQ::SOCKET_* constants.
      
persistent_id
       If persistent_id is specified the socket will be persisted over multiple requests.
       If context is not persistent the socket falls back to non-persistent mode.
      
on_new_socketCallback function, which is executed when a new socket structure is created. This function does not get invoked if the underlying persistent connection is re-used.
Example #1 A ZMQSocket() example
Using callback the bind/connect socket
<?php
/*
  The socket is persistent so this function is called only on the 
  first request to the script.
*/
function on_new_socket_cb(ZMQSocket $socket, $persistent_id = null)
{
    if ($persistent_id === 'server') {
        $socket->bind("tcp://localhost:12122");
    } else {
        $socket->connect("tcp://localhost:12122");
    }
}
/* Allocate a new context */
$context = new ZMQContext();
/* Create a new socket */
$socket = $context->getSocket(ZMQ::SOCKET_REP, 'server', 'on_new_socket_cb');
$message = $socket->recv();
echo "Received message: {$message}\n";
?>
The callback signature
Note:
function on_new_socket_cb(ZMQSocket $socket, string $persistent_id = null);
Throws ZMQSocketException on error.