Sliding Window SMS Sending Rate Limiting Algorithm in PHP with Redis

There are two sliding‑window rate‑limiting strategies for SMS sending: one based on the client IP address and another based on the mobile phone number.

1. IP‑address limits

1 minute limit: 5
10 minutes limit: 30
1 hour limit: 50

2. Phone‑number limits

1 minute limit: 1
10 minutes limit: 5
1 hour limit: 10

The following PHP code demonstrates how to enforce these limits using Redis sorted sets.

5,
    600  => 30,
    3600 => 50
);
// Phone rules
$phoneRules = array(
    60   => 1,
    600  => 5,
    3600 => 10
);
// Check limits based on IP
$r = checkLimits($ipRules, $_SERVER["REMOTE_ADDR"], $_GET['tel']);
var_dump($r);

// Check limits based on phone number
$r = checkLimits($phoneRules, $_GET['tel'], $_GET['tel']);
var_dump($r);

function checkLimits($rules, $key, $tel) {
    $redis = new Redis();
    $redis->connect('127.0.0.1', 6379);
    foreach ($rules as $ruleTime => $rule) {
        $redisKey = $key . "_" . $ruleTime;
        $score = time();
        $member = $tel . '_' . $score;
        $redis->multi();
        // Remove data outside the window
        $redis->zRemRangeByScore($redisKey, 0, $score - $ruleTime);
        $redis->zAdd($redisKey, $score, $member);
        $redis->expire($redisKey, $ruleTime);
        $redis->zRange($redisKey, 0, -1, true);
        $members = $redis->exec();
        if (empty($members[3])) {
            break;
        }
        $nums = count($members[3]);
        var_dump($nums);
        if ($nums > $rule) {
            return false;
        }
    }
    return true;
}
?>