How to get the user's ip address in php

IP Address: An Internet Protocol address (IP address) is a numerical label assigned to every device connected to a computer network that uses the Internet Protocol to communicate. An IP address has two main functions: host or network interface identification and location addressing.

$_SERVER['REMOTE_ADDR']: The IP address of the user’s computer browsing the current page

$_SERVER['HTTP_CLIENT_IP']: Client's ip (recommended learning: PHP programming from entry to proficiency)

$_SERVER['HTTP_X_FORWARDED_FOR']: Gateway of the user's computer browsing the current page

$_SERVER['HTTP_X_REAL_IP']: In nginx proxy mode, get the real IP of the client

/**
 * 获取客户端IP地址
 */
function real_ip()
{
  $ip = $_SERVER['REMOTE_ADDR'];
  if (isset($_SERVER['HTTP_X_FORWARDED_FOR']) && preg_match_all('#\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}#s', 
  $_SERVER['HTTP_X_FORWARDED_FOR'], $matches)) {
    foreach ($matches[0] AS $xip) {
      if (!preg_match('#^(10|172\.16|192\.168)\.#', $xip)) {
        $ip = $xip;
        break;
      }
    }
  } elseif (isset($_SERVER['HTTP_CLIENT_IP']) && preg_match('/^([0-9]{1,3}\.){3}[0-9]{1,3}$/', 
  $_SERVER['HTTP_CLIENT_IP'])) {
    $ip = $_SERVER['HTTP_CLIENT_IP'];
  } elseif (isset($_SERVER['HTTP_CF_CONNECTING_IP']) && preg_match('/^([0-9]{1,3}\.){3}[0-9]{1,3}$/', 
  $_SERVER['HTTP_CF_CONNECTING_IP'])) {
    $ip = $_SERVER['HTTP_CF_CONNECTING_IP'];
  } elseif (isset($_SERVER['HTTP_X_REAL_IP']) && preg_match('/^([0-9]{1,3}\.){3}[0-9]{1,3}$/', 
  $_SERVER['HTTP_X_REAL_IP'])) {
    $ip = $_SERVER['HTTP_X_REAL_IP'];
  }
  return $ip;
}

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