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checkdnsrr

(PHP 4, PHP 5, PHP 7, PHP 8)

checkdnsrrRésolution DNS d'une adresse IP

Description

checkdnsrr(string $hostname, string $type = "MX"): bool

Recherche l'enregistrement DNS de type type correspondant à l'hôte hostname.

Liste de paramètres

hostname

hostname peut être soit une adresse IP au format numérique, soit un nom d'hôte.

type

type peut être l'une des valeurs suivantes : A, MX, NS, SOA, PTR, CNAME, AAAA, A6, SRV, NAPTR, TXT ou ANY.

Valeurs de retour

Retourne true si un enregistrement a été trouvé, et false en cas d'erreur ou si aucun enregistrement n'a été trouvé.

Notes

Note:

Pour une compatibilité avec Windows avant son implémentation, essayez la classe » PEAR : » Net_DNS.

Voir aussi

  • dns_get_record() - Lit les données DNS associées à un hôte
  • getmxrr() - Retourne les enregistrements MX d'un hôte
  • gethostbyaddr() - Retourne le nom d'hôte correspondant à une IP
  • gethostbyname() - Retourne l'adresse IPv4 correspondant à un hôte
  • gethostbynamel() - Retourne la liste d'IPv4 correspondante à un hôte
  • la page du manuel man named(8)

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User Contributed Notes 6 notes

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34
Krisztin Ferenczi
10 years 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
up
15
Martin
7 years ago
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
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-1
n at zay dot uk
2 years ago
I always think you should state the blindingly obvious.
A function that contains checkdnsrr will return false without an internet connection.
So in a production environment you need an active internet connection to return a true result with a valid email address.
up
-1
Patrick
19 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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-6
criffoh at gmail dot com
10 years 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
up
-16
dobs
5 years ago
$this->_buf - for bulk check cache

function ValidateEmail($email)
{
list($user, $domain) = explode('@', $email);

if (!filter_var($email, FILTER_VALIDATE_EMAIL) !== FALSE)
return 0;

if (isset($this->_buf[$domain]))
return $this->_buf[$domain];

if (checkdnsrr($domain) === FALSE) {
$this->_buf[$domain] = 0;
return 0;
}
$this->_buf[$domain] = 1;

return 1;
}
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