What are some best practices for accurately capturing referrer data in PHP, considering factors like proxies and firewalls?

When capturing referrer data in PHP, it's important to account for factors like proxies and firewalls that can alter or hide the true referrer information. One way to accurately capture referrer data is by checking both the HTTP_REFERER server variable and the X-Forwarded-For header, which can provide more reliable information in cases where the referrer has been obscured. 

$referrer = isset($_SERVER['HTTP_REFERER']) ? $_SERVER['HTTP_REFERER'] : '';

if(isset($_SERVER['HTTP_X_FORWARDED_FOR']) && !empty($_SERVER['HTTP_X_FORWARDED_FOR'])){
    $forwardedFor = $_SERVER['HTTP_X_FORWARDED_FOR'];
    $ipList = explode(',', $forwardedFor);
    $referrer = trim(end($ipList));
}

echo "Referrer: " . $referrer;

Keywords

referrer data PHP proxies firewalls capturing

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