一个得到客户端IP的函数(PHP)

一个取得客户端IP的函数，是从osCommerce中取出来的，好象还是挺全面的，特意抄下来，以备后用。

<?php
function tep_get_ip_address() {
    if (isset($_SERVER)) {
      if (isset($_SERVER['HTTP_X_FORWARDED_FOR'])) {
        $ip = $_SERVER['HTTP_X_FORWARDED_FOR'];
      } elseif (isset($_SERVER['HTTP_CLIENT_IP'])) {
        $ip = $_SERVER['HTTP_CLIENT_IP'];
      } else {
        $ip = $_SERVER['REMOTE_ADDR'];
      }
    } else {
      if (getenv('HTTP_X_FORWARDED_FOR')) {
        $ip = getenv('HTTP_X_FORWARDED_FOR');
      } elseif (getenv('HTTP_CLIENT_IP')) {
        $ip = getenv('HTTP_CLIENT_IP');
      } else {
        $ip = getenv('REMOTE_ADDR');
      }
    }
    return $ip;
}
echo tep_get_ip_address();
?>