checkdnsrr

(PHP 4, PHP 5)

checkdnsrr Controlla i record DNS relativi ad un host Internet o indirizzo IP

Descrizione

int checkdnsrr ( string $host [, string $type ] )

Cerca i record DNS del tipo type corrispondenti a host. Restituisce vero se dei records sono trovati; falso se nessun record viene trovato o in caso di errore.

type può essere uno dei seguenti: A, MX, NS, SOA, PTR, CNAME, oppure ANY. Il default è MX.

Host può essere sia l'indirizzo IP in notazione decimale o il nome dell'host.

Nota: Questa funzione non è implementata sulle piattaforme Windows.

Vedere anche getmxrr(), gethostbyaddr(), gethostbyname(), gethostbynamel() e la man page named(8).

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User Contributed Notes 7 notes

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10
Patrick
9 years ago
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;

   }   
}

?>
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1
criffoh at gmail dot com
1 year ago
Is not possible validate domains with 'ñ' for my country.

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

ñandu.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('ñandu.cl', 'A')); // returns false
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0
Krisztin Ferenczi
1 year ago
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('ñandu.cl', 'A')); // returns false
var_dump(checkdnsrr(idn_to_ascii('ñandu.cl'), 'A')); // return true
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0
Anonymous
7 years ago
<?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;
}
?>
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-1
satmd
8 years ago
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.
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-1
fox dot 69 at gmx dot net
11 years ago
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; }
    }
}
?>
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-1
kriek at jonkriek dot com
11 years ago
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.
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