dns_get_record
(PHP 5 CVS only)
dns_get_record -- Fetch DNS Resource Records associated
with a hostname
Description
array dns_get_record ( string hostname [, int type [, array
&authns, array &addtl]])
Note: This function is not implemented on Windows platforms.
Try the PEAR class Net_DNS.
This function returns an array of associative arrays. Each
associative array contains at minimum the following keys:
Table 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_ALL or DNS_ANY. The default is DNS_ANY.
Note: 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.
Table 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
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.
Note: 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().
Example 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.
Example 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()
