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;
}