What is the significance of checking for the HTTP REFERER in PHP when handling banner clicks on a website?

Checking for the HTTP REFERER in PHP when handling banner clicks on a website is significant because it helps ensure that the click is coming from a valid source. This can prevent click fraud and unauthorized clicks on banners. By verifying the HTTP REFERER, you can make sure that the click is originating from your own website or an approved source.

if(isset($_SERVER['HTTP_REFERER']) && strpos($_SERVER['HTTP_REFERER'], 'yourwebsite.com') !== false) {
    // Handle the banner click
    // Redirect to the appropriate page
    header('Location: banner-clicked.php');
    exit();
} else {
    // Invalid click, handle accordingly (e.g. log the incident)
    echo 'Invalid click detected';
}