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How to set up analytics in PHP

Feb 21, 2024

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Product analytics enable you to gather and analyze data about how users interact with your PHP app. To show you how to set up analytics, in this tutorial we create a basic PHP app, add PostHog, and use it to capture events and create insights.

1. Create a basic PHP app

We start by creating a simple PHP app that has two pages:

  1. A login page where a user can enter their name, email, and company name in form.
  2. A dashboard page that has some text and a button.

First, ensure PHP is installed. Then, create a new folder for your project called php-analytics. In this folder, create two files index.php and dashboard.php:

Terminal
mkdir php-analytics
cd ./php-analytics
touch index.php
touch dashboard.php

Next, add the following code to index.php to set up a basic login page:

index.php
<!DOCTYPE html>
<html>
<head>
    <title>Login</title>
    <style>
        label, input, button {
            display: block;
            margin-bottom: 10px;
        }
    </style>
</head>
<body>
    <form action="auth.php" method="POST">
        <label for="name">Name:</label>
        <input type="text" name="name" required>


        <label for="email">Email:</label>
        <input type="email" name="email" required>


        <label for="company_name">Company Name:</label>
        <input type="text" name="company_name" required>


        <button type="submit">Log in</button>
    </form>
</body>
</html>

Then, set up the dashboard page:

dashboard.php
<?php
session_start();
?>


<!DOCTYPE html>
<html>
<head>
    <title>Dashboard</title>
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.6.0/jquery.min.js"></script>
</head>
<body>
    <h1>Welcome, <?php echo htmlspecialchars($_SESSION['name']); ?> from <?php echo htmlspecialchars($_SESSION['company_name']); ?>!</h1>


    <form id="dashboardForm" action="api/dashboard.php" method="POST">
        <input type="hidden" name="email" value="<?php echo htmlspecialchars($_SESSION['email']); ?>">
        <input type="hidden" name="name" value="<?php echo htmlspecialchars($_SESSION['name']); ?>">
        <input type="hidden" name="company_name" value="<?php echo htmlspecialchars($_SESSION['company_name']); ?>">
        <button type="submit">Click Me</button>
    </form>


    <script>
    $(document).ready(function() {
        $('#dashboardForm').on('submit', function(e) {
            e.preventDefault();
            $.ajax({
                url: $(this).attr('action'),
                type: 'POST',
                data: $(this).serialize(),
            });
        });
    });
    </script>
</body>
</html>

Then, create a new file auth.php to save the session details from the login page:

Terminal
touch auth.php
auth.php
<?php
session_start();


$_SESSION['email'] = $_POST['email'] ?? '';
$_SESSION['name'] = $_POST['name'] ?? '';
$_SESSION['company_name'] = $_POST['company_name'] ?? '';


header('Location: dashboard.php');
exit;

Lastly, we create an endpoint /api/dashboard.php which is called when the button on the dashboard page is clicked. This endpoint does nothing for now:

Terminal
mkdir api
cd ./api
touch dashboard.php
dashboard.php
<?php
// This is a placeholder file for the API endpoint.
// Later we will add logic here for when the button is clicked.

Run php -S localhost:8000 and navigate to http://localhost:8000 to see our app in action. Enter anything in the login page to save some session details.

2. Add PostHog to your app

With our app set up, it’s time to install and set up PostHog. If you don't have a PostHog instance, you can sign up for free.

To start, make sure Composer is installed. Then run composer require posthog/posthog-php to install PostHog’s PHP SDK.

Then, we initialize PostHog in api/dashboard.php. This is where we will add our event capture code in the next step of this tutorial.

api/dashboard.php
<?php
require_once __DIR__ . '/../vendor/autoload.php';
use PostHog\PostHog;


PostHog::init(
  '<ph_project_api_key>',
  ['host' => https://us.i.posthog.com]
);

You can find your project API key and instance address in your project settings.

With this set up, we're ready to capture events.

3. Implement the event capture code

To show how to capture events with PostHog, we capture an event when the button on the dashboard page is clicked. To do this, we call PostHog::capture():

api/dashboard.php
require_once __DIR__ . '/../vendor/autoload.php';
use PostHog\PostHog;


PostHog::init(
  '<ph_project_api_key>',
  ['host' => https://us.i.posthog.com]
);


session_start();
PostHog::capture([
  'distinctId' => $_SESSION['email'],
  'event' => 'home_api_called'
]);

With this set up, refresh your app and click the button on the dashboard page a few times. You should now see the captured event in your PostHog activity tab.

Feature flag created in PostHog

💡 PostHog tip: Setting the correct distinctId

When calling PostHog::capture, you need to provide a distinctID argument. This is a unique identifier for your user and enables you to correctly attribute events to them.

For logged-in users, you typically use their email or database ID. For logged-out or anonymous users, you should use a unique identifier, either generated by you or the PostHog JavaScript web library (which can then be accessed in the cookies. See an example of accessing the PostHog cookie in our Nuxt tutorial).

Setting event properties

When capturing events, you can optionally include additional information by setting the properties argument. This is helpful for breaking down or filtering events when creating insights.

To show an example, we add the user's name as an event property:

api/dashboard.php
PostHog::capture([
  'distinctId' => $_SESSION['email'],
  'event' => 'home_api_called',
  'properties' => [
    'user_name' => $_SESSION['name'],
  ]
]);

Capturing group events

Groups are a powerful feature in PostHog that aggregate events based on entities, such as organizations or companies. This is especially helpful for B2B SaaS apps, where often you want to view insights such as number of active companies or company churn rate.

To enable group analytics, you'll need to upgrade your PostHog account to include them. This requires entering your credit card, but don't worry, we have a generous free tier of 1 million events per month – so you won't be charged anything yet.

To create groups in PostHog, simply include them in your code when capturing events by setting the $groups argument:

api/dashboard.php
PostHog::capture([
  'distinctId' => $_SESSION['email'],
  'event' => 'home_api_called',
  'properties' => [
    'user_name' => $_SESSION['name'],
  ],
  '$groups' => [
    'company' => $_SESSION['company_name'],
  ]
]);

In the above example, we create a group type company, and then we set the value as the unique identifier for that specific company. This enables us to breakdown insights by company (we show you how to do this in the next section).

4. Create an insight in PostHog

Restart your app and capture events using different inputs in the login page. This will capture events for different users and companies and enable us to show the power of PostHog insights.

Next, go to the product analytics tab in PostHog and click the + New insight button. PostHog supports many different types of insights, such as trends, funnels, paths and more.

In this tutorial, we create a simple trend insight:

  1. Select the Trends tab.
  2. Under the Series header select the home_api_called event.
  3. Click on the Total count dropdown to change how events are aggregated. You can choose options such as Count per user, Unique users, Unique company(s), and more. You can also add filters or breakdown based on properties.

For example, in the image below we set our insight to show number of unique users that captured the home_api_called event where the user_name property is equal to Max:

Insight created in PostHog

That's it! Feel free to play around in your dashboard and explore the different kinds of insights you can create in PostHog.

Further reading