Tutorial

How to Set Up a Website Hit Counter With Redis and PHP on Ubuntu 20.04

Published on December 30, 2021

How to Set Up a Website Hit Counter With Redis and PHP on Ubuntu 20.04

The author selected the Apache Software Foundation to receive a donation as part of the Write for DOnations program.

Introduction

A hit counter is an application that records and indicates the number of visits your web page has received. The counter starts from 1 and is incremented once every time a web page is visited.

To keep track of the visits, the hit counter application requires a form of a database. While disk-based database management systems like MySQL can work, an in-memory database is better in terms of speed, performance, scalability, simplicity, and ease of use. This is where the Redis server comes into play. Redis stores data in your computer’s RAM instead of hitting the disk every time you’re performing an input/output operation. This increases the throughput significantly.

To track your site visits, you require a Redis hash map. This is a data structure that implements a key-value pair. A hash map provides a hash table that maps keys to values. Once a user visits your web page, you create a key based on their public IP address or username (for authenticated users), and then you initialize their total visits to a value of 1. Then, every time the user revisits your web page, you check their total visits from the Redis hash map based on their IP address/username and increment the value.

In this guide, you’ll set up a website hit counter with Redis and PHP on your Ubuntu 20.04 server. The PHP scripts in this guide use the visitors’ public IP addresses to track their visits.

Prerequisites

To follow along with this guide, make sure you have the following:

An Ubuntu 20.04 server configured using the Initial Server Setup with Ubuntu 20.04 guide.
A non-root user with sudo privileges. Follow our How To Create a New Sudo-enabled User on Ubuntu 20.04 [Quickstart] guide to set up a non-root sudo user.
Apache and PHP. To set up these, use our How To Install Linux, Apache, MySQL, PHP (LAMP) stack on Ubuntu 20.04 tutorial. You may skip Step 2 — Installing MySQL and Step 4 — Creating a Virtual Host for your Website since you don’t require a MySQL database or a virtual host to test this guide.
Redis server. Read our How To Install and Secure Redis on Ubuntu 20.04 [Quickstart] tutorial to install and secure a Redis server.

Step 1 — Installing PHP Redis Extension

In this step, you’ll install a Redis extension that allows PHP to talk to the Redis server. You’ll also create a test web page that implements the Redis hash map to track web visits.

Before installing the Redis extension, refresh your Ubuntu package information index:

sudo apt update

Then, run the following command to install php-redis. The extension provides an API for communicating with the Redis server key-value store:

sudo apt install -y php-redis

Restart Apache to load the new extension:

sudo systemctl restart apache2

You’ve now installed a PHP extension that talks to your Redis server. Next, you’ll create a test.php web page under the root directory of the Apache webserver. This is just a sample file that visitors request when they visit your website with a browser. Under the hood, the test.php page file loads a hit_counter.php script which you’ll later create to track page visits using the Redis server.

In a real-life scenario, your website might have tens or even hundreds of web pages. For this guide, you’ll set up a single web page for demonstration purposes.

In your terminal window, use nano to create a new test.php file under the root directory of your web-server /var/www/html/:

sudo nano /var/www/html/test.php

Then, enter the following information into the test.php file:

/var/www/html/test.php

<?php
  require_once 'hit_counter.php';
?>

<!DOCTYPE html>
<html>

  <head>
    <title>Sample Test Page</title>
  </head>

  <body>
    <h1>Sample test page</h1>
    <p>This is a sample test page.</p>
  </body>

</html>

Save and close the file when you’re through with editing. In this step, you’ve created a simple HTML web page that loads a hit_counter.php file when visited. Next, you’ll code the hit_counter.php file to track the test page visits.

Step 2 — Creating a Redis Hit Counter Script

When working in a production environment, it’s very conventional to separate re-usable PHP files. This allows you to implement the logic in these files on different parts of the project just by including their paths instead of copy-pasting the code. This makes maintenance easier since you only need to edit a single file in case you need to change the logic. This saves you a lot of time.

You’re going to apply the same strategy in this guide. You’ll create a single hit_counter.php file that you can include on any web page that requires visitors’ tracking.

In this file, you’ll use the php-redis library to connect to the Redis server from PHP. Then, you’ll create a Redis hash map to store the number of visits a visitor has made to your website. You’ll use the visitors’ unique IP addresses as Redis keys to distinguish each visitor’s hit counts in the Redis server.

In your terminal window, open a new hit_counter.php file using nano for editing purposes:

sudo nano /var/www/html/hit_counter.php

With the hit_counter.php file now created, open a new PHP tag <?php. Then, inside a try { block enter the following code to connect to your local Redis server on port 6379. Replace EXAMPLE_PASSWORD with the authentication password for the Redis server:

/var/www/html/hit_counter.php


<?php

    try {

        $redis = new Redis();
        $redis->connect('127.0.0.1', 6379);
        $redis->auth('EXAMPLE_PASSWORD');

Next, give the Redis hash map($siteVisitsMap) a name of your choice. This guide uses siteStats for demonstration purposes:

/var/www/html/hit_counter.php


        $siteVisitsMap = 'siteStats';

After defining the Redis hash map, you’ll now initialize an empty Redis key ($visitorHashKey). Then, you’ll populate it with the visitors’ IP addresses. You’ll use the value of the $visitorHashKey variable to uniquely identify each visitor requesting your web page:

/var/www/html/hit_counter.php



        $visitorHashKey = '';           

        if (!empty($_SERVER['HTTP_CLIENT_IP'])) {

            $visitorHashKey = $_SERVER['HTTP_CLIENT_IP'];

        } elseif (!empty($_SERVER['HTTP_X_FORWARDED_FOR'])) {

            $visitorHashKey = $_SERVER['HTTP_X_FORWARDED_FOR'];

        } else {

            $visitorHashKey = $_SERVER['REMOTE_ADDR'];
        }

In this code, you’re using the PHP if statement to determine the visitor’s IP address by checking whether the $_SERVER['HTTP_CLIENT_IP'], $_SERVER['HTTP_X_FORWARDED_FOR'], or $_SERVER['REMOTE_ADDR'] variables are populated.

Following this, initialize a $totalVisits variable to store the total visits for each IP address and assign it a value of 0. Then, use the PHP if (...) {...} else {...} and $redis->hExists($siteVisitsMap, $visitorHashKey) statements to check if the IP address has any entries in the Redis server.

You’ll use the statement if ($redis->hExists($siteVisitsMap, $visitorHashKey)) {...} to check whether a $visitorHashKey exists in a map named $siteVisitsMap.

In case the map and the key with the named IP address exist in the Redis server, retrieve it with the statement $visitorData = $redis->hMget($siteVisitsMap, array($visitorHashKey)); and use $totalVisits = $visitorData[$visitorHashKey] + 1; to increment the $totalVisits variable. You’re using the $redis->hMget statement to get hit count data associated with an IP address. The hMget function accepts the name of your map ($siteVisitsMap) and an array of the keys that you want to retrieve from the Redis server. In this case, you only have one key ($visitorHashKey), but you must convert it to an array using the statement array($visitorHashKey).

In case your script encounters the IP address for the first time, set the $totalVisits variable to 1. Finally, use $redis->hSet($siteVisitsMap, $visitorHashKey, $totalVisits); to set the value of the $visitorHashKey according to the results of the previous if (...) {...} else {...} statement. The $redis->hSet($siteVisitsMap, $visitorHashKey, $totalVisits) statement creates a $siteVisitsMap hash map in the Redis server with a key named $visitorHashKey with a value of $totalVisits.

Then, welcome the visitor by echoing the total visits and close the } catch (...) {...} block:

/var/www/html/hit_counter.php


        $totalVisits = 0;

        if ($redis->hExists($siteVisitsMap, $visitorHashKey)) {

            $visitorData = $redis->hMget($siteVisitsMap, array($visitorHashKey));
            $totalVisits = $visitorData[$visitorHashKey] + 1;

        } else {

            $totalVisits = 1;

        }

        $redis->hSet($siteVisitsMap, $visitorHashKey, $totalVisits);

        echo "Welcome, you've visited this page " .  $totalVisits . " times\n";

    } catch (Exception $e) {
        echo $e->getMessage();
    }

Once completed, your /var/www/html/hit_counter.php file should be similar to the following code:

/var/www/html/hit_counter.php


<?php

    try {

        $redis = new Redis();
        $redis->connect('127.0.0.1', 6379);
        $redis->auth('EXAMPLE_PASSWORD');

        $siteVisitsMap  = 'siteStats';
        $visitorHashKey = '';           

        if (!empty($_SERVER['HTTP_CLIENT_IP'])) {

           $visitorHashKey = $_SERVER['HTTP_CLIENT_IP'];

        } elseif (!empty($_SERVER['HTTP_X_FORWARDED_FOR'])) {

           $visitorHashKey = $_SERVER['HTTP_X_FORWARDED_FOR'];

        } else {

           $visitorHashKey = $_SERVER['REMOTE_ADDR'];
        }
      
        $totalVisits = 0;

        if ($redis->hExists($siteVisitsMap, $visitorHashKey)) {

            $visitorData = $redis->hMget($siteVisitsMap,  array($visitorHashKey));
            $totalVisits = $visitorData[$visitorHashKey] + 1;

        } else {

            $totalVisits = 1;

        }

        $redis->hSet($siteVisitsMap, $visitorHashKey, $totalVisits);

        echo "Welcome, you've visited this page " .  $totalVisits . " times\n";

    } catch (Exception $e) {
        echo $e->getMessage();
    }

Save and close the file when you’re through with editing. You’ve now coded a hit_counter.php script. Next, you’ll create another PHP script that generates a report from the data gathered in the Redis hash map.

Step 3 — Creating a Site Stats Report Script

Once you’ve collected data in a Redis hash map, it might not make any sense if you’re not able to retrieve and represent the information in a report. In this step, you’ll create a log report to show the different site visitors and the total visits they’ve made on the test web page.

To create the log report script, run nano on your terminal window and create a new /var/www/html/log_report.php file:

sudo nano /var/www/html/log_report.php

Then, enter the information below into the file. Replace EXAMPLE_PASSWORD with the correct password for the Redis server:

/var/www/html/log.php


<!DOCTYPE html>
<html>

  <head>
    <title>Site Visits Report</title>
  </head>

  <body>

      <h1>Site Visits Report</h1>

      <table border = '1'>
        <tr>
          <th>No.</th>
          <th>Visitor</th>
          <th>Total Visits</th>
        </tr>

        <?php

            try {

                $redis = new Redis();
                $redis->connect('127.0.0.1', 6379);
                $redis->auth('EXAMPLE_PASSWORD');

                $siteVisitsMap = 'siteStats';                          

                $siteStats = $redis->HGETALL($siteVisitsMap);

                $i = 1; 

                foreach ($siteStats as $visitor => $totalVisits) {

                    echo "<tr>";
                      echo "<td align = 'left'>"   . $i . "."     . "</td>";
                      echo "<td align = 'left'>"   . $visitor     . "</td>";
                      echo "<td align = 'right'>"  . $totalVisits . "</td>";
                    echo "</tr>";
                    
                    $i++;
                }

            } catch (Exception $e) {
                echo $e->getMessage();
            }

        ?>

      </table>
  </body>

</html>

Save and close the file when you’re through with editing. In the above script, you’re connecting to the Redis server and you’re using the statement $redis->HGETALL($siteVisitsMap); to retrieve your web page visits’ hash map. Then, you’re using the PHP foreach ($siteStats as $visitor => $totalVisits) { statement to loop and display the visitors’ IP addresses and the number of visits they’ve made to your site. You’re using the Redis HGETALL command to retrieve all fields (IP addresses) and values (total visits per each IP address) from the siteVisitsMap map.

You now have a test page, a hit counter script, and a report page to check your site stats. Next, you’ll test the functionalities of your hit counter and see if everything works.

Step 4 — Testing the Redis Hit Counter

In this step, you’ll test the whole logic for your hit counter. Navigate to the following URL on your web browser. Replace your-server-IP with your server’s public IP address or domain name.

http://your-server-IP/test.php

Refresh the page several times using different devices to generate enough stats. After each visit, you should receive the following output.

Next, visit the following URL to get your site visits report displayed in an HTML table

http://your-server-IP/log_report.php

You should now see a report similar to the following output.

Your hit counter is now working as expected.

Conclusion

In this guide, you’ve set up a website hit counter with Redis and PHP on your Ubuntu 20.04 server.

As you can see from the sample source code in this guide, Redis provides cleaner methods for creating and updating hash maps.

As mentioned at the beginning of this guide, using a relational database management system may still work but you’ll write tons of code to insert and update data in underlying tables. In addition, disk-based databases may experience scalability issues when your site grows.

For more information on using Redis in-memory database, follow the guides below:

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