A more easy way to count online users using php + apc/memcached or redis

apc.php

<?php
session_start();

// ref: http://expressjs.com/guide.html#users-online
function get_online_user($session_id) {
    if (false === ($online_users = apc_fetch("online/users"))) {
        $online_users = [];
    }

    $online_users[$session_id] = time();
    $now = time();

    foreach($online_users as $session_id => $last_activity) {
        if ($last_activity < $now - 60) {
            unset($online_users[$session_id]);
        }
    }
    apc_store("online/users", $online_users);
    return array(
        'count'    => count($online_users),
        'sessions' => array_keys($online_users),
    );
}

var_dump(get_online_user(session_id()));

redis.php

<?php
require 'predis/autoload.php';

function get_online_user($session_id) {
    $redis = new Predis\Client();

    $replies = $redis->pipeline(function($pipe) use($session_id) {
        $key = 'online/sessions';
        $now = time();
        $pipe->zadd($key, $now, $session_id);
        $pipe->zremrangebyscore($key, '-inf', $now - 300); // remove expired session
        $pipe->zcard($key);
        $pipe->zrevrange($key, 0, -1);
        // $pipe->zrevrange('online/users', 0, -1, 'WITHSCORES');
    });
    return array(
        'count' => $replies[2],
        'sessions'  => $replies[3],
    );
}

session_start();
echo "<pre>";
print_r(get_online_user(session_id()));
echo "</pre>";

also read:

• https://gist.github.com/lukemelia/279256#file-tracking-an-active-user-rb
• https://gist.github.com/diogok/955879
• http://stackoverflow.com/q/25007782/662170
• http://flask.pocoo.org/snippets/71/