How can a PHP developer ensure consistent and reliable display of referral data from users accessing a website, considering the variability in how browsers and servers handle this information?

To ensure consistent and reliable display of referral data from users accessing a website, a PHP developer can use server-side methods to extract and process the referral information. This involves accessing and parsing the HTTP_REFERER header, which contains the URL of the referring page. By handling this data on the server side, the developer can standardize the way referral information is captured and displayed, regardless of variations in browser behavior.

// Retrieve and sanitize the referral data from the HTTP_REFERER header
$referral = isset($_SERVER['HTTP_REFERER']) ? filter_var($_SERVER['HTTP_REFERER'], FILTER_SANITIZE_URL) : '';

// Display the referral data
echo "Referral URL: " . $referral;