Today, I came across this awesome post on the Spool blog—Fast, easy, realtime metrics using Redis bitmaps. And I immediately wanted to build something in PHP. You should read the article to get the background of what I am trying to do here.
First, Java has native a Bitset library. No such luck in PHP. So, after scouring, I found that PECL has here. Follow the instructions in the README to install the Bitset library. You might have to add the extension to your php.ini file manually:
extension=bitset.soNext, use a PHP-Redis client of Predis. Here’s the rest of the code sample:
<?php
//Check if the bitset extension is available:
if (!extension_loaded("bitset")) {
print "<font color='red'>[Fail]</font> Eep! The PECL Bitset extension is not installed/enabled.<br />";
exit;
}
//Start processing
print "<font color='green'>[OK]</font> PECL Bitset extension found!<br />";
//Load Predis
require "Predis/lib/Predis/Autoloader.php";
Predis\Autoloader::register();
$client = new \Predis\Client();
print "<font color='green'>[OK]</font> Predis loaded ok!<br />";
//Set the bitset
//Since this is a test, I will use a timestamp to create a unique Redis key so that the ouput produces is the same every time
$ts = date('U');
$key = "pageviews:homepage:$ts";
$client->setbit($key, 50, 1);
$client->setbit($key, 45, 1);
$client->setbit($key, 3, 1);
$client->setbit($key, 17, 1);
//Get the bitset
$pageCountBitset = $client->get($key);
//Delete the bitset to avoid cluttering your instance
$client->del($key);
print "<br />";
print "The raw bitset: " . bitset_to_string($pageCountBitset) . "<br/>";
print "Cardinality value: " . bitset_count($pageCountBitset) . " --> This is your number of pageviews<br/>";
?>This is, of course, a test and you wouldn’t normally use this to track page views real time. But it’s just an indication of the vast array of problems you can solve with Redis.