php 获取服务器的ip址址

/**
 * 获取服务器的ip
 * @access      public
 * @return string
 **/
function real_server_ip(){
 static $serverip = NULL;
 
 if ($serverip !== NULL){
  return $serverip;
 }
 
 if (isset($_SERVER)){
  if (isset($_SERVER['SERVER_ADDR'])){
   $serverip = $_SERVER['SERVER_ADDR'];
  }
  else{
   $serverip = '0.0.0.0';
  }
 }
 else{
  $serverip = getenv('SERVER_ADDR');
 }
 
 return $serverip;
}