Is $_SERVER['REMOTE_ADDR'] a Reliable Way to Identify Website Visitors?

Protecting Your Website: Can You Trust $_SERVER['REMOTE_ADDR']?

Every website interacts with numerous visitors, and identifying their origin is crucial. But how can you ensure the authenticity of the requesting IP address? The question arises: is $_SERVER['REMOTE_ADDR'] a reliable indicator?

Unveiling the Truth: Can Remote IP Addresses Be Spoofed?

Attempting to substitute the requesting IP address through headers or similar methods is futile. $_SERVER['REMOTE_ADDR'] provides the pristine source IP address of the TCP connection, effectively preventing manipulation.

Understanding the Risk of Proxy Servers

In certain scenarios, particularly when using reverse proxies, $_SERVER['REMOTE_ADDR'] might be susceptible to inaccuracies. Reverse proxies serve as intermediaries, forwarding requests to downstream servers while exposing their IP address as REMOTE_ADDR. To obtain the genuine user IP address, headers like X-Forwarded-For must be consulted.

The Impact on Access Control

The reliability of $_SERVER['REMOTE_ADDR'] has profound implications for access control. For instance, consider the following snippet:

if ($_SERVER['REMOTE_ADDR'] == '222.222.222.222') {
    $grant_all_admin_rights = true;
}

As established, $_SERVER['REMOTE_ADDR'] is secure, making this approach valid for granting specific privileges based on IP address.

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