Skip to main content

tracking email opens using PHP

The standard and most common method for tracking email opens using PHP involves embedding a hidden, unique 1x1 pixel image in the HTML body of the email. When the recipient opens the email and their email client loads images, it sends a request to your server, which logs the open event. 

Limitations and Considerations
  • Image Blocking: Many email clients (like some versions of Outlook) block images by default. The email will not be tracked unless the user specifically chooses to "display images".
  • Privacy: This method is a common marketing tactic but may be blocked by users with enhanced privacy settings.
  • Gmail Image Caching: Gmail often caches images on its own servers, so you will know the email was opened, but the IP address logged will be Google's server, not the recipient's.
  • Reliability: It is not a 100% reliable method, but it is the most widely used for statistical purposes. 

Implementation Steps
This implementation requires two PHP scripts and a database (e.g., MySQL) to store the email status. 

1. The Tracking Script (tracker.php) 
This script is called when the hidden image is loaded. It logs the open event in your database and then serves a transparent 1x1 pixel image back to the client. 

php
<?php
// email_track.php or tracker.php
$connect = new PDO("mysql:host=localhost;dbname=your_database_name", "your_username", "your_password");

if (isset($_GET["code"])) {
    $track_code = $_GET["code"];
    $open_datetime = date("Y-m-d H:i:s");
    $ip_address = $_SERVER['REMOTE_ADDR']; // Note: may log Google's IP for Gmail users
    $user_agent = $_SERVER['HTTP_USER_AGENT'];

    // Update the database record associated with the unique tracking code
    $query = "
        UPDATE email_data 
        SET email_status = 'yes', 
            email_open_datetime = :open_datetime,
            opener_ip = :ip_address,
            opener_user_agent = :user_agent
        WHERE email_track_code = :track_code AND email_status = 'no'
    ";
    
    $statement = $connect->prepare($query);
    $statement->execute([
        ':open_datetime' => $open_datetime,
        ':ip_address' => $ip_address,
        ':user_agent' => $user_agent,
        ':track_code' => $track_code
    ]);
}

// Serve a 1x1 transparent GIF image
header('Content-Type: image/gif');
header('Content-Length: 43'); // Length of a 1x1 transparent GIF

// A single-pixel transparent GIF data (base64 decoded)
echo base64_decode('R0lGODlhAQABAJAAAP8AAAAAACH5BAUQAAAALAAAAAABAAEAAAICBAEAOw==');
exit;
?>

2. The Email Sending Script (send_email.php) 
When you send the email, you generate a unique tracking code and include the URL to tracker.php in the HTML body. 
You'll need to generate a unique tracking code for each email, create the HTML body including a hidden image that links to your tracker.php script with the unique code, and log the email details in your database before sending. Using a library like PHPMailer is recommended for sending the email. The following code provides an example: 

php
<?php
// send_email.php
// ... (setup database connection and base URL) ...
// ... (gather recipient info, subject, body, etc.) ...

$track_code = md5(uniqid(rand(), true)); // Generate a unique code

$email_body = '<html><body>';
$email_body .= '<p>Email content here.</p>';

// Embed the hidden 1x1 tracking image
$email_body .= '<img src="' . $base_url . 'tracker.php?code=' . $track_code . '" width="1" height="1" style="display:none !important; min-height:1px; width:1px; border:0; -webkit-appearance:none; mso-hide:all;" alt="" />';
$email_body .= '</body></html>';

// Log the email in the database before sending (example using prepared statement)
// ... (database insert query and execution using $track_code and other email data) ...

// Use PHPMailer to send the HTML email
// ... (PHPMailer configuration, set subject, body, recipient, and send) ...
?>

3. Database Structure
A table, such as email_data, is required to store information about sent emails and their open status. The table should include columns for the email subject, body, recipient address, the unique tracking code, the open status, and details about the opener like the datetime, IP, and user agent. You can find an example SQL structure in the original response. 
Back to top