Special Sending Rule - Skip Duplicates Per Day

gistfile1.php

# This special sending rule will prevent the same email address from receiving
# more than one email per day from campaigns that are configured to use this
# rule.
#
# It has no affect on:
#
#   (1) campaigns that don't use this SSR 
#   (2) autoresponders.

# We want "today" to be in the "America/Chicago" time zone.
date_default_timezone_set("America/Chicago");

# This function either:
#
#   (1) grabs a previously allocated connection to a local Redis server
#   (2) connects to the local Redis server
function GetGlobalRedis () {
    global $globalRedis;
    
    if ( is_null($globalRedis) ) {
        $globalRedis = new Redis();
        $globalRedis->connect("127.0.0.1", 6379);
    }
    
    return $globalRedis;
}

# This function does the following:
#
#   (1) Test if the email has already received a message today.
#   (2) Mark that this email has received a message today.
#   (3) Expire the key tracking this email after 48 hours.
function HasEmailReceivedToday ($email) {
    $redis      = GetGlobalRedis();
    $today      = strftime("%Y-%m-%d");
    $keyExpire  = 60 * 60 * 48; // 48 hours, in seconds
    $key        = "HasEmailReceivedToday:$today:$email";
    $didReceive = $redis->getset($key, "1") === "1";

    $redis->expire($key, $keyExpire);
    
    return $didReceive;
}

# This is the actual execution of the special sending rule. For each recipient,
# we want to skip it if it's already received an email today.
return array_map((function ($recipient) use ($campaign_information_hash) {

  $email      = $recipient->subscriber->email;
  $didReceive = HasEmailReceivedToday($email);
  $skip       = $didReceive ? 1 : 0;

  return array('skip' => $skip);

}), $multiple_recipients_information_hash);