checkdnsrr

(PHP 4, PHP 5, PHP 7)

checkdnsrr — 给指定的主机（域名）或者IP地址做DNS通信检查

说明

bool checkdnsrr ( string $host [, string $type = "MX" ] )

根据不同记录（type）类型查询主机（host）相应的DNS记录。

参数

host

主机（host）可以是一个IP地址也可以是域名。

type

解析记录类型（type）可能是下面这些类型中的任何一个：A，MX，NS，SOA，PTR，CNAME，AAAA，A6， SRV，NAPTR，TXT 或者 ANY。

返回值

如果记录能找到，就返回TRUE；如果查找不到该DNS记录或者发生了错误，就返回FALSE。

更新日志

版本 说明
5.3.0 这个函数在Windows平台上也可以使用了。
5.2.4 增加了TXT的记录类型。
5.0.0 增加了AAAA的记录类型。

注释

Note:

出于对低版本在windows平台上的兼容性，可以试试» PEAR扩展包里面提供的 » Net_DNS类。

参见

User Contributed Notes

Martin 30-Sep-2016 07:02
Important Warning:

You need to add a dot to the end of the host name to make a fully qualified domain name.

To see why, try executing the following pieces of code:

$d1="gmail.con";
$d2="gmail.con.";
$r1=checkdnsrr($d1, "MX");
$r2=checkdnsrr($d2, "MX");
var_dump($r1);
var_dump($r2);

You will see that without the dot it claims that the domain "gmail.con" is valid.

Note that if you time the "checkdnsrr()" calls you will also see it takes longer without the dot because it treats it as a relative domain and does several tries based on the host name it is running on.

NB: in case you're interested, being treated as a relative domain explains what is happening. If your host is "example.com" the relative domain will eventually resolve to "gmail.con.com." which can be looked up, hence it wrongly claims "gmail.con" exists
mshallop at linux dot com 26-Aug-2015 07:46
Updated (eregi is deprecated) function to validate an email and a domain.  Function allows for either fully-qualified email addresses, or partial address (@gmail.com or gmail.com).   Also supports the I18N character conversion.

 I'm using the function for white/black list content validation:

function checkEmailAndDomain($_email)
{
    $exp = "/^(.*)@(.*)$/";
    preg_match($exp, $_email, $matches);

    if (!empty($matches[1]) and (!filter_var($_email, FILTER_VALIDATE_EMAIL)))
        return (false);

    return (checkdnsrr(idn_to_ascii($matches[2]), 'MX'));
}
Anonymous 30-Mar-2015 07:21
Attention! By default the function searches only for MX records, when no type is specified. To search for any record you have to manually ask for it.

I hope i spared someone my day of bug searching caused by that oversight. :(
Krisztin Ferenczi 27-Oct-2013 08:12
criffoh at gmail dot com is right. Before you check domain, you must convert to ascii with idn_to_ascii function:
http://us2.php.net/manual/en/function.idn-to-ascii.php .

var_dump(checkdnsrr('?andu.cl', 'A')); // returns false
var_dump(checkdnsrr(idn_to_ascii('?andu.cl'), 'A')); // return true
criffoh at gmail dot com 18-Jul-2013 11:57
Is not possible validate domains with '?' for my country.

In my country is possible to register domain using '?' character. For example:

?andu.cl
http://nic.cl/cgi-bin/dom-CL?q=%F1andu

If I use this function to check DNS record, it return false, but the domain already exists:

var_dump(checkdnsrr('?andu.cl', 'A')); // returns false
12-Dec-2006 01:06
<?php
function check_dnsbl($ip)
{
    $dnsbl_check=array("bl.spamcop.net","list.dsbl.org",
"sbl.spamhaus.org",'xbl.spamhaus.org');
    if($ip){
        $rip=implode('.',array_reverse(explode(".",$ip)));
        foreach($dnsbl_check as $val){
            if(checkdnsrr($rip.'.'.$val.'.','A'))
                return $rip.'.'.$val;
        }
    }
    return false;
}
?>
satmd 28-Jan-2006 05:29
fox dot 69 at gmx dot net: I wonder where you got this code from. I have written this piece of code half a year ago and released it WITH a copyright header that is missing now! Anyways... this code is to be considered licenced "as-is", however it'd be nice to keep the authors note (This is something about reputation, you see?). Thanks.

(Much) more recent version of it:
<?php
function is_blacklisted($ip) {
   // written by satmd, do what you want with it, but keep the author please
   $result=Array();
   $dnsbl_check=array("bl.spamcop.net",
                       "list.dsbl.org",
                       "sbl.spamhaus.org");
   if ($ip) {
       $quads=explode(".",$ip);
       $rip=$quads[3].".".$quads[2].".".$quads[1].".".$quads[0];
       for ($i=0; $i<count($dnsbl_check); $i++) {
           if (checkdnsrr($rip.".".$dnsbl_check[$i].".","A")) {
              $result[]=Array($dnsbl_check[$i],$rip.".".$dnsbl_check[$i]);
           }
         }
      return $result;
   }
}
?>

Beware that this code's signature differs from the original! I also removed osirusoft as its results are not useful anyways (false positives!). Please make sure that you have nscd or a caching dns server running as this code is prone to (d)dos! Only use it in places where it is necessary (when data is to be modified), e.g. the script processing uploads/posts/replies in a blog.
Patrick 14-Dec-2004 04:53
This is a little code example that will validate an email address in two ways:
- first the general syntax of the string is checked with a regular expression
- then the domain substring (after the '@') is checked using the 'checkdnsrr' function

<?php

function validate_email($email){

   $exp = "^[a-z\'0-9]+([._-][a-z\'0-9]+)*@([a-z0-9]+([._-][a-z0-9]+))+$";

   if(eregi($exp,$email)){

      if(checkdnsrr(array_pop(explode("@",$email)),"MX")){
        return true;
      }else{
        return false;
      }

   }else{

      return false;

   }   
}

?>
fox dot 69 at gmx dot net 01-May-2003 10:40
maybe usefull, a blacklist (DNSBL) check function:

<?php
function is_blacklisted($ip) {
    $dnsbl_check=array("bl.spamcop.net",
                       "relays.osirusoft.com",
                       "list.dsbl.org",
                       "sbl.spamhaus.org");
    if ($ip) {
       $quads=explode(".",$ip);
        $rip=$quads[3].".".$quads[2].".".$quads[1].".".$quads[0];
        for ($i=0; $i<count($dnsbl_check); $i++) {
            if (checkdnsrr($rip.".".$dnsbl_check[$i],"A")) {
                $listed.=$dnsbl_check[$i]." ";
            }
         }
       if ($listed) { return $listed; } else { return FALSE; }
    }
}
?>
kriek at jonkriek dot com 26-Mar-2003 02:08
The checkdnsrr function is not implemented on the Windows platform. The way to get around this problem is to write your own version of checkdnsrr. Example: myCheckDNSRR

<?php
function myCheckDNSRR($hostName, $recType = '')
{
 if(!empty($hostName)) {
   if( $recType == '' ) $recType = "MX";
   exec("nslookup -type=$recType $hostName", $result);
   // check each line to find the one that starts with the host
   // name. If it exists then the function succeeded.
   foreach ($result as $line) {
     if(eregi("^$hostName",$line)) {
       return true;
     }
   }
   // otherwise there was no mail handler for the domain
   return false;
 }
 return false;
}
?>
Note that the type parameter is optional, and if you don't supply it then the type defaults to "MX" (which means Mail Exchange). If any records are found, the function returns TRUE. Otherwise, it returns FALSE.