Are there any limitations to using $_SERVER["HTTP_REFERER"] for obtaining the referrer URL in PHP?

One limitation of using $_SERVER["HTTP_REFERER"] is that it may not always be reliable as it can be easily manipulated or spoofed by the user. To enhance security and reliability, it is recommended to validate and sanitize the referrer URL before using it in your application.

// Validate and sanitize the referrer URL
$referrer = isset($_SERVER["HTTP_REFERER"]) ? filter_var($_SERVER["HTTP_REFERER"], FILTER_VALIDATE_URL) : null;

// Check if the referrer URL is valid
if ($referrer) {
    // Use the sanitized referrer URL in your application
    echo "Referrer URL: " . $referrer;
} else {
    echo "Invalid referrer URL";
}