Persistent local domain socket in php

Question

The answers I've found to this question (such as here , here , and here ) all involve pfsockopen(), which seems geared to non-local socket connections. However, the code I've written so far uses php to access a C++ server through a local connection. I want this connection to be persistent (so that I can use it for Comet, incidentally). Here's my non-persistent version:

<?php
session_start();

...

if (($sock = socket_create(AF_UNIX, SOCK_STREAM,0)) === false)
{
echo "socket_create() failed: reason: " . socket_strerror(socket_last_error()) . "\n";
        exit();
}
$sess_id = $_SESSION['sess_id'];
$sock_str = '/tmp/sockdir/' . $sess_id; //The socket is named after the php session, not important
if (socket_connect($sock, $sock_str) === false)
{
        echo "socket_connect() to " . $sock_str . " failed: reason: " . socket_strerror(socket_last_error($sock)) . "\n";
        socket_close($sock);
        exit();
}

$msg = $_GET['message'];

// ... do things with $msg

socket_close($sock);
?>

Now I can't simply save '$sock' as a $_SESSION variable and simply access it each time this script is called, I've found. Any tips on what I can do to turn this into a persistent connection?

Answer 1

As the links you provided point out, php is not a persistent language and there is no way to have persistence across sessions (ie page loads). You can create a middle ground though by running a second php script as a daemon, and have your main script (ie the one the user hits) connect to that (yes - over a socket...) and get data from it.

If you were to do that, and want to avoid the hassel of Web Sockets, try the new HTML5 EventStream API , as it gives you the best of both worlds: A commet like infrastructure without the hackyness of long-polling or the need for a dedicated Web Sockets server.

Answer 2

If you need to keep the connection open, you need to keep the PHP script open. Commonly PHP is just invoked and then closed after the script has run (CGI, CLI), or it's a mixture (mod_php in apache, FCGI) in which sometimes the PHP interpreter stays in memory after your script has finished (so everything associated from the OS to that process would still remain as a socket handle).

However this is never save. Instead you need to make PHP a daemon which can keep your PHP scripts in memory. An existing solution for that is Appserver-In-PHP . It will keep your code in memory until you restart the server. Like the code, you can as well preserve variables between requests, eg a connection handle.