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Last updated: Sat, 27 Jan 2007

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# dns_get_record

(PHP 5)

dns_get_record -- Fetch DNS Resource Records associated with a hostname

## Description

array dns_get_record ( string hostname [, int type [, array &authns, array &addtl]] )

> Замечание: This function is not implemented on Windows platforms, nor does it (currently) work on *BSD systems. Try the PEAR class Net_DNS.

This function returns an array of associative arrays. Each associative array contains at minimum the following keys:

Таблица 1. Basic DNS attributes

Attribute | Meaning
--- | ---
host | The record in the DNS namespace to which the rest of the associated data refers.
class | dns_get_record() only returns Internet class records and as such this parameter will always return `IN`.
type | String containing the record type. Additional attributes will also be contained in the resulting array dependant on the value of type. See table below.
ttl | Time To Live remaining for this record. This will not equal the record's original ttl, but will rather equal the original ttl minus whatever length of time has passed since the authoritative name server was queried.

`hostname` should be a valid DNS hostname such as "www.example.com". Reverse lookups can be generated using in-addr.arpa notation, but gethostbyaddr() is more suitable for the majority of reverse lookups.

By default, dns_get_record() will search for any resource records associated with `hostname`. To limit the query, specify the optional `type` parameter. `type` may be any one of the following: `DNS_A`, `DNS_CNAME`, `DNS_HINFO`, `DNS_MX`, `DNS_NS`, `DNS_PTR`, `DNS_SOA`, `DNS_TXT`, `DNS_AAAA`, `DNS_SRV`, `DNS_NAPTR`, `DNS_A6`, `DNS_ALL` or `DNS_ANY`. The default is DNS_ANY.

> Замечание: Because of eccentricities in the performance of libresolv between platforms, `DNS_ANY` will not always return every record, the slower `DNS_ALL` will collect all records more reliably.

The optional third and fourth arguments to this function, `authns` and `addtl` are passed by reference and, if given, will be populated with Resource Records for the Authoritative Name Servers, and any Additional Records respectively. See the example below.

Таблица 2. Other keys in associative arrays dependant on 'type'

Type | Extra Columns
--- | ---
`A` | `ip`: An IPv4 addresses in dotted decimal notation.
`MX` | `pri`: Priority of mail exchanger. Lower numbers indicate greater priority. `target`: FQDN of the mail exchanger. See also dns_get_mx().
`CNAME` | `target`: FQDN of location in DNS namespace to which the record is aliased.
`NS` | `target`: FQDN of the name server which is authoritative for this hostname.
`PTR` | `target`: Location within the DNS namespace to which this record points.
`TXT` | `txt`: Arbitrary string data associated with this record.
`HINFO` | `cpu`: IANA number designating the CPU of the machine referenced by this record. `os`: IANA number designating the Operating System on the machine referenced by this record. See IANA's Operating System Names for the meaning of these values.
`SOA` | `mname`: FQDN of the machine from which the resource records originated. `rname`: Email address of the administrative contain for this domain. `serial`: Serial # of this revision of the requested domain. `refresh`: Refresh interval (seconds) secondary name servers should use when updating remote copies of this domain. `retry`: Length of time (seconds) to wait after a failed refresh before making a second attempt. `expire`: Maximum length of time (seconds) a secondary DNS server should retain remote copies of the zone data without a successful refresh before discarding. `minimum-ttl`: Minimum length of time (seconds) a client can continue to use a DNS resolution before it should request a new resolution from the server. Can be overridden by individual resource records.
`AAAA` | `ipv6`: IPv6 address
`A6`(PHP >= 5.1.0) | `masklen`: Length (in bits) to inherit from the target specified by `chain`. `ipv6`: Address for this specific record to merge with `chain`. `chain`: Parent record to merge with `ipv6` data.
`SRV` | `pri`: (Priority) lowest priorities should be used first. `weight`: Ranking to weight which of commonly prioritized `targets` should be chosen at random. `target` and `port`: hostname and port where the requested service can be found. For additional information see: RFC 2782
`NAPTR` | `order` and `pref`: Equivalent to `pri` and `weight` above. `flags`, `services`, `regex`, and `replacement`: Parameters as defined by RFC 2915.

> Замечание: Per DNS standards, email addresses are given in user.host format (for example: hostmaster.example.com as opposed to hostmaster@example.com), be sure to check this value and modify if necessary before using it with a functions such as mail().

Пример 1. Using dns_get_record()

`<?php $result = dns_get_record("php.net"); print_r($result); ?>`

Produces output similar to the following:

    Array
    (
        [0] => Array
            (
                [host] => php.net
                [type] => MX
                [pri] => 5
                [target] => pair2.php.net
                [class] => IN
                [ttl] => 6765
            )

        [1] => Array
            (
                [host] => php.net
                [type] => A
                [ip] => 64.246.30.37
                [class] => IN
                [ttl] => 8125
            )

    )

Since it's very common to want the IP address of a mail server once the MX record has been resolved, dns_get_record() also returns an array in `addtl` which contains associate records. `authns` is returned as well containing a list of authoritative name servers.

Пример 2. Using dns_get_record() and DNS_ANY

`<?php
/* Request "ANY" record for php.net,
and create $authns and $addtl arrays
containing list of name servers and
any additional records which go with
them */
$result = dns_get_record("php.net", DNS_ANY, $authns, $addtl);
echo "Result = ";
print_r($result);
echo "Auth NS = ";
print_r($authns);
echo "Additional = ";
print_r($addtl);
?>`

Produces output similar to the following:

    Result = Array
    (
        [0] => Array
            (
                [host] => php.net
                [type] => MX
                [pri] => 5
                [target] => pair2.php.net
                [class] => IN
                [ttl] => 6765
            )

        [1] => Array
            (
                [host] => php.net
                [type] => A
                [ip] => 64.246.30.37
                [class] => IN
                [ttl] => 8125
            )

    )
    Auth NS = Array
    (
        [0] => Array
            (
                [host] => php.net
                [type] => NS
                [target] => remote1.easydns.com
                [class] => IN
                [ttl] => 10722
            )

        [1] => Array
            (
                [host] => php.net
                [type] => NS
                [target] => remote2.easydns.com
                [class] => IN
                [ttl] => 10722
            )

        [2] => Array
            (
                [host] => php.net
                [type] => NS
                [target] => ns1.easydns.com
                [class] => IN
                [ttl] => 10722
            )

        [3] => Array
            (
                [host] => php.net
                [type] => NS
                [target] => ns2.easydns.com
                [class] => IN
                [ttl] => 10722
            )

    )
    Additional = Array
    (
        [0] => Array
            (
                [host] => pair2.php.net
                [type] => A
                [ip] => 216.92.131.5
                [class] => IN
                [ttl] => 6766
            )

        [1] => Array
            (
                [host] => remote1.easydns.com
                [type] => A
                [ip] => 64.39.29.212
                [class] => IN
                [ttl] => 100384
            )

        [2] => Array
            (
                [host] => remote2.easydns.com
                [type] => A
                [ip] => 212.100.224.80
                [class] => IN
                [ttl] => 81241
            )

        [3] => Array
            (
                [host] => ns1.easydns.com
                [type] => A
                [ip] => 216.220.40.243
                [class] => IN
                [ttl] => 81241
            )

        [4] => Array
            (
                [host] => ns2.easydns.com
                [type] => A
                [ip] => 216.220.40.244
                [class] => IN
                [ttl] => 81241
            )

    )

See also dns_get_mx(), and dns_check_record()

add a note User Contributed Notes
dns_get_record
marcus at synchromedia dot co dot uk
01-Feb-2006 04:02
`The docs say "nor does it (currently) work on *BSD systems". Unfortunately this includes MacOS X. It's just not there in my build of 5.1.2 running on 10.4.4.`
ed at noxserver dot com
24-Mar-2005 05:44
`I recently needed to do some name server and IP discovery on the fly.
Server and domain monitoring system. If you've got a system with dig
the below seems to work fine for discovering name server and a
addresses. Shouldn't be hard for you to modify it for the other records if
needed.
$_REQUEST[url] = "http://www.example.com/";
$url_parts = parse_url($_REQUEST[url]);
$dns = Dig($url_parts[host]);
print_r($dns[name_servers]);
print_r($dns[ips]);
function Dig ($domain) {
$dig = `dig $domain`;
preg_match_all("/in\s+ns\s+(.+?)\s+/is"
,$dig,$name_servers,PREG_PATTERN_ORDER);
preg_match_all("/$domain.\s+[0-9]+\s+in\s+a\s+([0-9.]+)\s+/is"
,$dig,$ips,PREG_PATTERN_ORDER);
$dns[name_servers] = $name_servers[1];
$dns[ips] = $ips[1];
return($dns);
}`
axelm-php at nona dot net
16-May-2003 05:06
`I've done a backport of the function to PHP4.
It is available as extension at:
http://nona.net/software/dns_get_record/
comments & feedback appreciated.
--
Alexander Mayrhofer
axelm-php@nona.net`
add a note
fsockopen dns_get_mx

Last updated: Sat, 27 Jan 2007
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