(PHP 5, PHP 7, PHP 8)
dns_get_record — 獲取指定主機的DNS記錄
$hostname,$type = DNS_ANY,&$authns = ?,&$addtl = ?,&$raw = false
獲取指定主機（hostname）的DNS記錄。
hostname
主機名（hostname）應該是一個DNS解析生效的域名，例如“www.example.com”。主機名也可以是通過對逆向解析域做DNS逆向域名解析而得到，但是在大多數(shù)情況下gethostbyaddr()更加適合做逆向域名解析。
注意:
每個DNS標準，郵件地址必須是
user.host這樣的格式（例如hostmaster.example.com而不是hostmaster@example.com），在使用mail()這個函數(shù)之前請檢查這個值，有必要的話還需要修改。
type
默認情況下，dns_get_record()將會搜索所有與hostname相關(guān)的記錄，可以通過設(shè)置type來限定查詢。type的值可以是下面的其中的任何一個： 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或者DNS_ANY。
注意:
由于dns在各個平臺上表現(xiàn)有些不一樣，
DNS_ANY不會總是返回所有的記錄，DNS_ALL雖然慢一些，但是會得到所有的記錄，所以使用DNS_ALL更加可靠些。
authns以引用方式傳遞，如果寫了該參數(shù)，那么將會得到該解析記錄的DNS服務(wù)器（Authoritative Name Servers）的信息。
addtl以引用方式傳遞，如果填寫了該參數(shù)，將會得到其他所有的DNS解析記錄。
raw在原生模式下，在進行額外的查詢的時候之前我們只執(zhí)行請求的DNS類型，而不是循環(huán)查詢所有的類型。
這個函數(shù)返回一個關(guān)聯(lián)數(shù)組，如果失敗則 或者在失敗時返回 false。每個關(guān)聯(lián)數(shù)組都至少包含了以下的這些鍵。
at minimum the following keys:
| 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.
|
| 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.
|
| 版本 | 說明 |
|---|---|
| 5.4.0 |
增加了參數(shù)raw。
|
| 5.3.0 | 可以是在windows平臺上使用這個函數(shù)了。 |
| 5.3.0 |
在此版本之前，如果給參數(shù)authns傳入值，則必須同時傳入addtl的值。
|
示例 #1 使用 dns_get_record()函數(shù)
<?php
$result = dns_get_record("php.net");
print_r($result);
?>
以上例程的輸出類似于：
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
)
)
示例 #2 使用dns_get_record()配合DNS_ANY的例子
由于我們經(jīng)常會想獲取一個郵件服務(wù)器的對應的IP地址的MX記錄是否已經(jīng)生效。在使用dns_get_record()函數(shù)之后，addtl能夠返回一個相關(guān)的數(shù)組記錄，authns參數(shù)則會返回授權(quán)服務(wù)器的列表信息。
<?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);
?>
以上例程的輸出類似于：
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
)
)