Description
hostname - The name to lookup (eg. www.php.net)
type - The record type to query
class - The zone class to query
Constructs a DNS query packet and forwards the query to a
nameserver configured in the system stub resolver (ie.
/etc/resolv.conf). When a response is received from the DNS
server, a fully populated Net_DNS_Packet object is returned
that represents the response.
The resolver object contains many properties that control
that behaviour of the resolver. Some of these settings
are automatically read from the system resolver
configuration if available. On Linux/UNIX based systems,
this includes /etc/resolv.conf as well as various
environment variables. This configuration is done at the
time of object instantiation and can be overridden by
setting the appropriate object properties.
This function will only return a Net_DNS_Packet if the
ANSWER section contains resource records. Specifically,
if the ANCOUNT variable in the DNS packet header is 0,
query() will return 0 (note: 0, not FALSE). If you are
expecting a packet without resource records in the
ANSWER section, use Net_DNS_Resolver::rawQuery().
This is useful when doing manual recursion.
For a description of the returned RR data object, see
Net_DNS_RR.
Resolver Configuration Object Properties:
array $nameservers
An array of nameserver IP addresses that should be
queried.
int $port
The port on which nameservers should be queried. The default is 53.
array $domain
The domain in which the resolver client host resides.
array $searchlist
An array of strings containingg domains to apply to unqualified hosts
passed to the resolver.
int $retry
The number of seconds between retransmission of unaswered queries
int $retrans
The number of times unanswered requests should be retried
int $recurse
Sets the value of the RD (recursion desired) bit in the header. If the
RD bit is set to 0, the server will not perform recursion on the
request.
int $usevc
Whether or not to use TCP (Virtual Circuits) instead of UDP If set
to 0, UDP will be used unless TCP is required. TCP is required for
questions or responses greater than 512 bytes.
int $debug
If set to TRUE (non-zero), debugging code will be displayed as the
resolver makes the request.
Environment Variables:
RES_NAMESERVERS
Space separated list of nameserver IP addresses
to query
RES_SEARCHLIST
Space separated list of domain names to add to
unqualified search requests.
LOCALDOMAIN
The name of the domain
RES_OPTIONS
A space separated list of options formatted as:
optionname:value
If the value is ommited, the value defaults to 1
(true). [optionname] corresponds to an object
property.
Example
Example 48-1. Using Net_DNS_Resolver::query() <?php
require_once 'Net/DNS.php';
$resolver = new Net_DNS_Resolver();
$response = $resolver->query('example.com');
if ($response) {
foreach ($response->answer as $rr) {
$rr->display();
}
}
?> |
Output:
example.com. 129808 IN A 192.0.34.166 |
|
The following example shows a DNS query for an MX record.
Note that the IP address for the mail exchanger listed
within the zone is returned with the response in the
additional section. The second exchanger (that is not
inside this zone) is not listed. To receive this
address, you must perform another query specifically for
the A record using the returned hostname.
Example 48-2. Using Net_DNS_Resolver::query() to look up an MX record <?php
require_once 'Net/DNS.php';
$resolver = new Net_DNS_Resolver();
$response = $resolver->query('php.net', 'MX');
if ($response) {
foreach ($response->answer as $rr) {
$rr->display();
}
if (count($response->additional)) {
foreach ($response->additional as $rr) {
$rr->display();
}
}
}
?> |
Output:
php.net. 86121 IN MX 15 smtp.osuosl.org.
php.net. 86121 IN MX 5 osu1.php.net.
osu1.php.net. 86121 IN A 140.211.166.39 |
|
The next example shows a more complex query with
debugging information enabled. Note that the usevc
option is set to TRUE. This forces the resolver to use
TCP instead of UDP. This can be seen in the debug output
on the send_tcp() line.
Example 48-3. Using Net_DNS_Resolver::query() with specific nameservers and options <?php
require_once 'Net/DNS.php';
$resolver = new Net_DNS_Resolver();
$resolver->debug = 1; // Turn on debugging output to show the query
$resolver->usevc = 1; // Force the use of TCP instead of UDP
$resolver->nameservers = array( // Set the IP addresses
'198.41.0.4', // of the nameservers
'192.228.79.201' // to query.
);
$response = $resolver->query('example.com');
if (! $response) {
echo "\n";
echo "ANCOUNT is 0, therefore the query() 'failed'\n";
echo "See Net_DNS_Resolver::rawQuery() to receive this packet\n";
}
?> |
Output:
;; query(example.com, A, IN)
;; send_tcp(198.41.0.4:53)
;; sending 29 bytes
;; received 517 bytes
;; HEADER SECTION
;; id = 58298
;; qr = 1 opcode = QUERY aa = 0 tc = 0 rd = 1
;; ra = 0 rcode = NOERROR
;; qdcount = 1 ancount = 0 nscount = 13 arcount = 15
;; QUESTION SECTION (1 record)
;;
;example.com. IN A
;; ANSWER SECTION (0 records)
;; AUTHORITY SECTION (13 records)
com. 172800 IN NS A.GTLD-SERVERS.NET.
com. 172800 IN NS G.GTLD-SERVERS.NET.
com. 172800 IN NS H.GTLD-SERVERS.NET.
com. 172800 IN NS C.GTLD-SERVERS.NET.
com. 172800 IN NS I.GTLD-SERVERS.NET.
com. 172800 IN NS B.GTLD-SERVERS.NET.
com. 172800 IN NS D.GTLD-SERVERS.NET.
com. 172800 IN NS L.GTLD-SERVERS.NET.
com. 172800 IN NS F.GTLD-SERVERS.NET.
com. 172800 IN NS J.GTLD-SERVERS.NET.
com. 172800 IN NS K.GTLD-SERVERS.NET.
com. 172800 IN NS E.GTLD-SERVERS.NET.
com. 172800 IN NS M.GTLD-SERVERS.NET.
;; ADDITIONAL SECTION (15 records)
A.GTLD-SERVERS.NET. 172800 IN AAAA 2001:503:a83e::2:30
A.GTLD-SERVERS.NET. 172800 IN A 192.5.6.30
G.GTLD-SERVERS.NET. 172800 IN A 192.42.93.30
H.GTLD-SERVERS.NET. 172800 IN A 192.54.112.30
C.GTLD-SERVERS.NET. 172800 IN A 192.26.92.30
I.GTLD-SERVERS.NET. 172800 IN A 192.43.172.30
B.GTLD-SERVERS.NET. 172800 IN AAAA 2001:503:231d::2:30
B.GTLD-SERVERS.NET. 172800 IN A 192.33.14.30
D.GTLD-SERVERS.NET. 172800 IN A 192.31.80.30
L.GTLD-SERVERS.NET. 172800 IN A 192.41.162.30
F.GTLD-SERVERS.NET. 172800 IN A 192.35.51.30
J.GTLD-SERVERS.NET. 172800 IN A 192.48.79.30
K.GTLD-SERVERS.NET. 172800 IN A 192.52.178.30
E.GTLD-SERVERS.NET. 172800 IN A 192.12.94.30
M.GTLD-SERVERS.NET. 172800 IN A 192.55.83.30
ANCOUNT is 0, therefore the query() 'failed'
See Net_DNS_Resolver::rawQuery() to receive this packet |
|
