How to Reliably Get a Client's IP Address in PHP?

Getting Client IP Address in PHP

Before exploring methods to obtain the client IP address, it's crucial to understand why using only $_SERVER['REMOTE_ADDR'] may lead to incorrect results. Proxies, firewalls, or other intermediaries can alter the original IP address.

To address this issue, here are alternative approaches:

Using GETENV()

The getenv() function allows us to access environment variables. The following function employs it:

// Function to get client IP address
function get_client_ip() {
    $ipaddress = '';
    if (getenv('HTTP_CLIENT_IP'))
        $ipaddress = getenv('HTTP_CLIENT_IP');
    else if (getenv('HTTP_X_FORWARDED_FOR'))
        $ipaddress = getenv('HTTP_X_FORWARDED_FOR');
    //... (Other conditions omitted for brevity)
    else
        $ipaddress = 'UNKNOWN';
    return $ipaddress;
}

Using $_SERVER

PHP also provides the $_SERVER superglobal to access server variables. Here's a similar implementation using it:

// Function to get client IP address
function get_client_ip() {
    $ipaddress = '';
    if (isset($_SERVER['HTTP_CLIENT_IP']))
        $ipaddress = $_SERVER['HTTP_CLIENT_IP'];
    else if (isset($_SERVER['HTTP_X_FORWARDED_FOR']))
        $ipaddress = $_SERVER['HTTP_X_FORWARDED_FOR'];
    //... (Other conditions omitted for brevity)
    else
        $ipaddress = 'UNKNOWN';
    return $ipaddress;
}

Both of these functions consider multiple server variables to obtain the most accurate IP address available. They prioritize variables such as HTTP_CLIENT_IP and HTTP_X_FORWARDED_FOR, which provide higher reliability.

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