PHP根据IP实现城市切换或跳转

function GetIpLookup($ip = ''){  
  if(empty($ip)){  
    return '请输入IP地址'; 
  }  
  $res = @file_get_contents('http://int.dpool.sina.com.cn/iplookup/iplookup.php?format=js&ip=' . $ip);  
  if(empty($res)){ return false; }  
  $jsonMatches = array();  
  preg_match('#\{.+?\}#', $res, $jsonMatches);  
  if(!isset($jsonMatches[0])){ return false; }  
  $json = json_decode($jsonMatches[0], true);  
  if(isset($json['ret']) && $json['ret'] == 1){  
    $json['ip'] = $ip;  
    unset($json['ret']);  
  }else{  
    return false;  
  }  
  return $json;  
} 
$ipInfos = GetIpLookup('123.125.114.144'); //baidu.com IP地址  
var_dump($ipInfos);

function getIpAddress(){  
  $ipContent  = file_get_contents("http://int.dpool.sina.com.cn/iplookup/iplookup.php?format=js");  
  $jsonData = explode("=",$ipContent);   
  $jsonAddress = substr($jsonData[1], 0, -1);  
  return $jsonAddress;  
}  
$ip_info=json_decode(getIpAddress());

//根据IP地址跳转指定页面js取得城市
var city='<?echo ipCity($xp_UserIp);?>'; //根据IP地址所有城市跳转到指定页面
if(city.indexOf("上海市")>=0){
         window.location.href="http://shanghai.demo.com/"; }

<script src="/ipcity/ipaddress.php" type="text/javascript" language="javascript"></script>