(PHP 4, PHP 5, PHP 7)
checkdnsrr — Check DNS records corresponding to a given Internet host name or IP address
$host
[, string $type = "MX"
] )
Searches DNS for records of type type
corresponding to host.
host
host may either be the IP address in
dotted-quad notation or the host name.
type
type may be any one of: A, MX, NS, SOA,
PTR, CNAME, AAAA, A6, SRV, NAPTR, TXT or ANY.
Returns TRUE if any records are found; returns FALSE if no records
were found or if an error occurred.
| Version | Description |
|---|---|
| 5.3.0 | This function is now available on Windows platforms. |
| 5.2.4 |
TXT type was added.
|
Note:
For compatibility with Windows before this was implemented, then try the » PEAR class » Net_DNS.
criffoh at gmail dot com is right. Before you check domain, you must convert to ascii with idn_to_ascii function:
http://us2.php.net/manual/en/function.idn-to-ascii.php .
var_dump(checkdnsrr('ñandu.cl', 'A')); // returns false
var_dump(checkdnsrr(idn_to_ascii('ñandu.cl'), 'A')); // return true
This is a little code example that will validate an email address in two ways:
- first the general syntax of the string is checked with a regular expression
- then the domain substring (after the '@') is checked using the 'checkdnsrr' function
<?php
function validate_email($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("@",$email)),"MX")){
return true;
}else{
return false;
}
}else{
return false;
}
}
?>
Is not possible validate domains with 'ñ' for my country.
In my country is possible to register domain using 'ñ' character. For example:
ñandu.cl
http://nic.cl/cgi-bin/dom-CL?q=%F1andu
If I use this function to check DNS record, it return false, but the domain already exists:
var_dump(checkdnsrr('ñandu.cl', 'A')); // returns false
Updated (eregi is deprecated) function to validate an email and a domain. Function allows for either fully-qualified email addresses, or partial address (@gmail.com or gmail.com). Also supports the I18N character conversion.
I'm using the function for white/black list content validation:
function checkEmailAndDomain($_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'));
}
<?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;
}
?>
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. :(
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 $listed; } else { return FALSE; }
}
}
?>
fox dot 69 at gmx dot net: I wonder where you got this code from. I have written this piece of code half a year ago and released it WITH a copyright header that is missing now! Anyways... this code is to be considered licenced "as-is", however it'd be nice to keep the authors note (This is something about reputation, you see?). Thanks.
(Much) more recent version of it:
<?php
function is_blacklisted($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 $result;
}
}
?>
Beware that this code's signature differs from the original! I also removed osirusoft as its results are not useful anyways (false positives!). Please make sure that you have nscd or a caching dns server running as this code is prone to (d)dos! Only use it in places where it is necessary (when data is to be modified), e.g. the script processing uploads/posts/replies in a blog.
The checkdnsrr function is not implemented on the Windows platform. The way to get around this problem is to write your own version of checkdnsrr. Example: myCheckDNSRR
<?php
function myCheckDNSRR($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.
