我们先来看下个人常用的代码PHP
<?phpinclude_once("./qqwry.php");$QQWry=new QQWry; function get_real_ip(){$ip=false;if(!empty($_SERVER["HTTP_CLIENT_IP"])){$ip = $_SERVER["HTTP_CLIENT_IP"];}if (!empty($_SERVER["HTTP_X_FORWARDED_FOR"])) {$ips = explode (", ", $_SERVER["HTTP_X_FORWARDED_FOR"]);if ($ip) { array_unshift($ips, $ip); $ip = FALSE; }for ($i = 0; $i < count($ips); $i++) {if (!eregi ("^(10|172.16|192.168).", $ips[$i])) {$ip = $ips[$i];break;}}}return $ip;} function is_ip($str) { $ip = explode(".", $str); if (count($ip)<4 || count($ip)>4) return 0; foreach($ip as $ip_addr) { if ( !is_numeric($ip_addr) ) return 0; if ( $ip_addr<0 || $ip_addr>255 ) return 0; } return 1;} $ip=$_SERVER["REMOTE_ADDR"]; $ifErr=$QQWry->QQWry($ip); $city = $QQWry->Country.$QQWry->Local; //echo $city;*/ if (strpos($city,"玄武区")!==false){ $city = "玄武区";}else if(strpos($city,"仙林")!==false){ $city = "仙林";}else if(strpos($city,"秦淮区")!==false){ $city = "秦淮区";}else if(strpos($city,"江宁")!==false){ $city = "江宁";}else if(strpos($city,"鼓楼")!==false){ $city = "鼓楼";}else{ $city = "栖霞";}if (isset($_GET["chengshi"])) { //Ê×Ïȼì²âÊÇ·ñ»ñµÃÁË GET ´«µÝµÄÊý¾Ý setcookie("cookie_city",$_GET["chengshi"],time()+3600*24);$city = $_GET["chengshi"]; } else if (isset($_COOKIE["cookie_city"])) { //¼ì²âÊÇ·ñ´æÔÚêdzÆCookie $city = $_COOKIE["cookie_city"]; //ÏÔʾCookie±£´æµÄÊý¾Ý } else { setcookie("cookie_city",$city,time()+3600*24); //´¿³õʼ»¯´Ë±äÁ¿ $_COOKIE["cookie_city"] = $city;} ?>HTML
<!DOCTYPE html><html lang="zh-cn"><head><meta charset="utf-8"/><LINK href="css/css.css" type=text/css rel=stylesheet><SCRIPT src="js/jquery-1.4.2.min.js" type=text/javascript></SCRIPT><title>城市切换</title></head><BODY><DIV class=selCity id=allCity style="DISPLAY: none"><DIV class=area><TABLE> <TBODY> <TR> <TD><A class=cur href="show.html">玄武区</A></TD> <TD><A href="show1.html">仙林</A></TD> <TD><A href="show2.html">秦淮区</A></TD> <TD><A href="show3.html">鼓楼</A></TD> <TD><A href="show4.html">江宁</A></TD> <TD><A href="show5.html">栖霞区</A></TD> </TR> </TBODY></TABLE><DIV class=none><A id=foldin href="javascript:;">全部</A></DIV></DIV></DIV><DIV class=header> <DIV class=area> <DIV class=r> <DIV class="topCtiy clear"> <UL> <LI class=i1><A href="index.php">全部小区</A></LI> <LI class=i1> <?php echo $city; ?> </LI> <LI class=i2 id=changeCity>切换城市</LI> </UL> </DIV> </DIV> </DIV></DIV><SCRIPT type=text/javascript>jQuery(function(){ $("#changeCity").click(function(a){ $("#allCity").slideDown(300); a.stopPropagation(); $(this).blur(); }); $("#allCity").click(function(a){ a.stopPropagation() }); $(document).click(function(a){ a.button!=2 && $("#allCity").slideUp(300) }); $("#foldin").click(function(){ $("#allCity").slideUp(300) });});</SCRIPT></body></html>另外附上网友的实现方法：使用方法：解压后QQWry.Dat就是我们想要IP地址数据库，我们新建一个ipcity文件夹，将数据库放在下面。QQ IP数据库使用非常方便，数据也很齐全，你可以及时关注官方更新以保持数据最新，强力推荐一下：）接下来，我们在上面的ipcity目录下新建一个ipaddress.php文件，直接复制以下代码进去即可，重要的地方也作了相应注释。B段：
<?/*函数名称：ipCity参数说明：$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:leecontact: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 $useripaddr;}?>PHP根据IP地址实现城市切换或跳转到这里，其实问题已经很简单了，用简单的js就通通搞定。C段如下：
//根据IP地址跳转指定页面js取得城市var city="<?echo ipCity($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/";}将开头的A段代码和上面的C段代码分别放在B段代码的头和尾，然后我们在需要跳转的页面加入以下代码：<script src="/ipcity/ipaddress.php" type="text/javascript" language="javascript"></script>刷新页面，是不是达到预想的效果了呢？以上就是PHP获取IP地址、PHP根据IP地址判断城市以及PHP根据IP地址实现城市切换或跳转的详细介绍了，事实上，像PHP中通过IP地址自动切换城市就是这个方法的典型应用。举一反三，我们通过这种方法，也可以实现屏蔽指定IP地址或城市的用户访问，自己研究一下吧，也挺简单的：）
