PHP中根据IP地址判断城市实现城市切换或跳转代码

<?php
function getip() {
    if ($_server["http_x_forwarded_for"])
        $ip = $_server["http_x_forwarded_for"];
    else if ($_server["http_client_ip"])
        $ip = $_server["http_client_ip"];
    else if ($_server["remote_addr"])
        $ip = $_server["remote_addr"];
    else if (getenv("http_x_forwarded_for"))
        $ip = getenv("http_x_forwarded_for");
    else if (getenv("http_client_ip"))
        $ip = getenv("http_client_ip");
    else if (getenv("remote_addr"))
        $ip = getenv("remote_addr");
    else
        $ip = "unknown";
    return $ip;
}
echo getip();
?>

function getip ()
{
                if (getenv('http_client_ip')) {
                        $ip = getenv('http_client_ip');
                } else if (getenv('http_x_forwarded_for')) {
                        $ip = getenv('http_x_forwarded_for');
                } else if (getenv('remote_addr')) {
                        $ip = getenv('remote_addr');
                } else {
                        $ip = $_server['remote_addr'];
                }
                return $ip;

<?
/*
函数名称：ipcity
参数说明：$userip——用户ip地址
函数功能：php通过ip地址判断用户所在城市
author:lee
contact:xpsem2010@gmail.com
*/
function ipcity($userip) {
    //ip数据库路径，这里用的是qq ip数据库 20110405 纯真版
    $dat_path = 'qqwry.dat';
    //判断ip地址是否有效
    if(!ereg("^([0-9]{1,3}.){3}[0-9]{1,3}$", $userip)){
        return 'ip address invalid';
    }
    //打开ip数据库
    if(!$fd = @fopen($dat_path, 'rb')){
        return 'ip data file not exists or access denied';
    }
    //explode函数分解ip地址，运算得出整数形结果
    $userip = explode('.', $userip);
    $useripnum = $userip[0] * 16777216 + $userip[1] * 65536 + $userip[2] * 256 + $userip[3];
    //获取ip地址索引开始和结束位置
    $databegin = fread($fd, 4);
    $dataend = fread($fd, 4);
    $useripbegin = implode('', unpack('l', $databegin));
    if($useripbegin < 0) $useripbegin += pow(2, 32);
    $useripend = implode('', unpack('l', $dataend));
    if($useripend < 0) $useripend += pow(2, 32);
    $useripallnum = ($useripend - $useripbegin) / 7 + 1;
    $beginnum = 0;
    $endnum = $useripallnum;
    //使用二分查找法从索引记录中搜索匹配的ip地址记录
    while($userip1num>$useripnum || $userip2num<$useripnum) {
        $middle= intval(($endnum + $beginnum) / 2);
        //偏移指针到索引位置读取4个字节
        fseek($fd, $useripbegin + 7 * $middle);
        $useripdata1 = fread($fd, 4);
        if(strlen($useripdata1) < 4) {
            fclose($fd);
            return 'file error';
        }
        //提取出来的数据转换成长整形，如果数据是负数则加上2的32次幂
        $userip1num = implode('', unpack('l', $useripdata1));
        if($userip1num < 0) $userip1num += pow(2, 32);
        //提取的长整型数大于我们ip地址则修改结束位置进行下一次循环
        if($userip1num > $useripnum) {
            $endnum = $middle;
            continue;
        }
        //取完上一个索引后取下一个索引
        $dataseek = fread($fd, 3);
        if(strlen($dataseek) < 3) {
            fclose($fd);
            return 'file error';
        }
        $dataseek = implode('', unpack('l', $dataseek.chr(0)));
        fseek($fd, $dataseek);
        $useripdata2 = fread($fd, 4);
        if(strlen($useripdata2) < 4) {
            fclose($fd);
            return 'file error';
        }
        $userip2num = implode('', unpack('l', $useripdata2));
        if($userip2num < 0) $userip2num += pow(2, 32);
        //找不到ip地址对应城市
        if($userip2num < $useripnum) {
            if($middle == $beginnum) {
                fclose($fd);
                return 'no data';
            }
            $beginnum = $middle;
        }
    }
    $useripflag = fread($fd, 1);
    if($useripflag == chr(1)) {
        $useripseek = fread($fd, 3);
        if(strlen($useripseek) < 3) {
            fclose($fd);
            return 'system error';
        }
        $useripseek = implode('', unpack('l', $useripseek.chr(0)));
        fseek($fd, $useripseek);
        $useripflag = fread($fd, 1);
    }
    if($useripflag == chr(2)) {
        $addrseek = fread($fd, 3);
        if(strlen($addrseek) < 3) {
            fclose($fd);
            return 'system error';
        }
        $useripflag = fread($fd, 1);
        if($useripflag == chr(2)) {
            $addrseek2 = fread($fd, 3);
            if(strlen($addrseek2) < 3) {
                fclose($fd);
                return 'system error';
            }
            $addrseek2 = implode('', unpack('l', $addrseek2.chr(0)));
            fseek($fd, $addrseek2);
        } else {
            fseek($fd, -1, seek_cur);
        }
        while(($char = fread($fd, 1)) != chr(0))
            $useripaddr2 .= $char;
        $addrseek = implode('', unpack('l', $addrseek.chr(0)));
        fseek($fd, $addrseek);
        while(($char = fread($fd, 1)) != chr(0))
            $useripaddr1 .= $char;
    } else {
        fseek($fd, -1, seek_cur);
        while(($char = fread($fd, 1)) != chr(0))
            $useripaddr1 .= $char;
        $useripflag = fread($fd, 1);
        if($useripflag == chr(2)) {
            $addrseek2 = fread($fd, 3);
            if(strlen($addrseek2) < 3) {
                fclose($fd);
                return 'system error';
            }
            $addrseek2 = implode('', unpack('l', $addrseek2.chr(0)));
            fseek($fd, $addrseek2);
        } else {
            fseek($fd, -1, seek_cur);
        }
        while(($char = fread($fd, 1)) != chr(0)){
            $useripaddr2 .= $char;
        }
    }
    fclose($fd);
    //返回ip地址对应的城市结果
    if(preg_match('/http/i', $useripaddr2)) {
        $useripaddr2 = '';
    }
    $useripaddr = "$useripaddr1 $useripaddr2";
    $useripaddr = preg_replace('/cz88.net/is', '', $useripaddr);
    $useripaddr = preg_replace('/^s*/is', '', $useripaddr);
    $useripaddr = preg_replace('/s*$/is', '', $useripaddr);
    if(preg_match('/http/i', $useripaddr) || $useripaddr == '') {
        $useripaddr = 'no data';
    }
    return $useripaddr;
}
?>

var city='<?echo ipcity($xp_userip);?>';

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>