PHP中根据IP地址判断城市实现城市切换或跳转代码

d, 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))