Question

I have a simple web page in which the user will enter some information before submitting the form. I would like to retrieve his IPaddress after the post is done.

Answer 1

Here is function from another relevant post that should help:

function getUserIpAddr()
{
    if (!empty($_SERVER['HTTP_CLIENT_IP'])) //if from shared
    {
        return $_SERVER['HTTP_CLIENT_IP'];
    }
    else if (!empty($_SERVER['HTTP_X_FORWARDED_FOR']))   //if from a proxy
    {
        return $_SERVER['HTTP_X_FORWARDED_FOR'];
    }
    else
    {
        return $_SERVER['REMOTE_ADDR'];
    }
}

This will cover the occasional proxy user and shared networks.