获取主机名的ip地址或在php中将主机名转换为ip地址

我有一个脚本，使用api来获取ip地址的ip信息。我得到一个问题的IP地址的域名或主机名或转换为IP，我正在寻找一个代码来解决这个问题，所以当访问者来到网站可以磁带或寻找IP和域名，并获得IP的域名和相关信息，谢谢你。

index . php

<?php
require_once('ipapi.class.php');
if(isset($_GET['ip']))
$rip = $_GET['ip'];
else
$rip = $_REQUEST['REMOTE_ADDR']; // the IP address to query
$query = IPAPI::query("$rip");
echo "'t IP Information: " .$rip. "<br />";
echo "'t ISP: " .$query->isp . "<br />";
echo "'t Organization: " .$query->org . "<br />";
echo "'t City: " .$query->city . "<br />";
echo "'t Region: " .$query->regionName . "<br />";
echo "'t Country: " .$query->country . "<br />"; 
?>
<form name="input" action="#" method="get">
IP: <input type="text" name="ip">
<input type="submit" value="Submit">
</form>

ipapi.class.php

 if (getenv("HTTP_CLIENT_IP") && strcasecmp(getenv("HTTP_CLIENT_IP"), "unknown")) 
 { 
    $rip = getenv("HTTP_CLIENT_IP"); 
 } 
 else if (getenv("HTTP_X_FORWARDED_FOR") && strcasecmp(getenv("HTTP_X_FORWARDED_FOR"), "unknown")) 
 { 
    $rip = getenv("HTTP_X_FORWARDED_FOR"); 
 } 
 else if (getenv("REMOTE_ADDR") && strcasecmp(getenv("REMOTE_ADDR"), "unknown")) 
 { 
    $rip = getenv("REMOTE_ADDR"); 
 } 
 else if (isset($_SERVER['REMOTE_ADDR']) && $_SERVER['REMOTE_ADDR'] &&       strcasecmp($_SERVER['REMOTE_ADDR'], "unknown")) 
 { 
    $rip = $_SERVER['REMOTE_ADDR']; 
 } 
 else 
 { 
    $rip = "unknown"; 
 } 

PS: rip = ip我将其命名为rip而不是ip