thinkphp how to get the client IP_php tips

In the thinkphp framework, the system has a built-in get_client_ip method to obtain the client’s IP address. Usage example:
$ip = get_client_ip();
In addition to thinkphp's built-in get_client_ip function, you can also use the following function to obtain the client IP address.
$type indicates the return type 0 returns the IP address, 1 returns the IPV4 address number
Share the code as follows

function get_client_ip($type = 0) {
  $type    = $type ? 1 : 0;
  static $ip =  NULL;
  if ($ip !== NULL) return $ip[$type];
  if (isset($_SERVER['HTTP_X_FORWARDED_FOR'])) {
    $arr  =  explode(',', $_SERVER['HTTP_X_FORWARDED_FOR']);
    $pos  =  array_search('unknown',$arr);
    if(false !== $pos) unset($arr[$pos]);
    $ip   =  trim($arr[0]);
  }elseif (isset($_SERVER['HTTP_CLIENT_IP'])) {
    $ip   =  $_SERVER['HTTP_CLIENT_IP'];
  }elseif (isset($_SERVER['REMOTE_ADDR'])) {
    $ip   =  $_SERVER['REMOTE_ADDR'];
  }
  // IP地址合法验证
  $long = ip2long($ip);
  $ip  = $long ? array($ip, $long) : array('0.0.0.0', 0);
  return $ip[$type];

I hope this article will be helpful for everyone to learn more about PHP programming.