php/redis rate limiter and blacklist handler

redis-rate-limiter.php

<?php
/**
 * Based on https://engineering.classdojo.com/blog/2015/02/06/rolling-rate-limiter/
 */

for ($i = 1; $i < 20; $i++) {
    
    // limit 5 runs of action by ip every 10 seconds, runs function if overflown
    limit('action', 'ip', 5, 10, function($count) {
        echo "Ran limit function after $count runs";
    });
}

// check if 'user' or 'ip' are banned (FALSE)
var_dump(banned(['user', 'ip']));

// ban 'user'
ban("user", "misbehave", 10);

// check if 'user' or 'ip' are banned ('user' is)
var_dump(banned(['user', 'ip']));

// ban 'ip'
ban("ip", "ip banned", 10);

// check if 'user' or 'ip' are banned (both are)
var_dump(banned(['user', 'ip']));

// ---
// Functions
// ---

/**
 * Singleton, returns a Redis instance
 * @return Redis
 */
function redis() {
    static $redis;

    if(!$redis) {

        $redis = new Redis();

        $redis->connect("redis", 6379);

    }

    return $redis;
}


/**
 * Bans $key for $ttl seconds
 * @param $key
 * @param int $ttl
 */
function ban($key, $reason = "banned", $ttl = 600) {
    $redis = redis();

    $redis->set("ban:$key", $reason);

    $redis->expire("ban:$key", $ttl);
}

/**
 * Check if any of the $keys are banned
 * @param array $keys
 * @return bool|string ban reason or FALSE if not banned
 */
function banned(array $keys) {
    $redis = redis();

    $mGet = array_map(function($item) { return "ban:$item"; }, $keys);

    $reason = implode(",", array_filter($redis->mget($mGet), function($item) {
        return $item !== FALSE;
    }));

    return strlen($reason) ? $reason : FALSE;
}

/**
 * Limits $action by $client to $threshold occurrencies within the last $ttl seconds
 * @param $action
 * @param $client
 * @param $threshold
 * @param int $ttl
 * @param callable
 * @return int
 */
function limit($action, $client, $threshold, $ttl = 60, $fn = null) {
    $key = "$action:$client";

    $ts = microtime(true) * 10000;

    $redis = redis();

    // expire old entries
    $redis->zRemRangeByScore($key,0, $ts - $ttl * 10000);

    // count entries
    $count = $redis->zCount($key, 0, $ts);

    if($fn && $count >= $threshold) {
        return call_user_func($fn, $count);
    }
    else {
        // add new entry
        $redis->zAdd($key, $ts, $ts);

        $redis->expire($key, $ttl);

        return $count + 1;
    }
}