What are potential differences in how Apache and IIS servers handle HTTP_REFERER information in PHP?

When using PHP to access the HTTP_REFERER information in Apache and IIS servers, there may be differences in how the information is handled due to server configurations. To ensure consistent handling of HTTP_REFERER information across different servers, it is recommended to check if the information is set before using it in your code. 

if(isset($_SERVER['HTTP_REFERER'])){
    $referer = $_SERVER['HTTP_REFERER'];
    // Use $referer variable in your code
} else {
    // Handle case where HTTP_REFERER is not set
}

Keywords

Apache IIS HTTP_REFERER server PHP

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