dns_get_record

(PHP 5, PHP 7, PHP 8)

dns_get_record — 获取指定主机名的 DNS 纪录

说明

dns_get_record(
    string $hostname,
    int $type = DNS_ANY,
    array &$authoritative_name_servers = null,
    array &$additional_records = null,
    bool $raw = false
): array|false

获取指定 hostname 的 DNS 纪录。

参数

hostname: hostname 应该是有效的 DNS 主机名，比如“www.example.com”。可以使用 in-addr.arpa 表示法生成反向查找，但大多数情况下更适合用 gethostbyaddr()。

注意:
根据 DNS 标准，邮件地址以 user.host 格式给出（例如：hostmaster.example.com 而不是 hostmaster@example.com），请务必检查此值并在必要时进行修改，然后将其与 mail() 等函数一起使用。
type: 默认情况下，dns_get_record() 将会搜索跟 hostname 关联的任何资源记录。要限制查询，可以指定可选的 type 选项。可以是以下之一：DNS_A、DNS_CNAME、DNS_HINFO, DNS_CAA、DNS_MX、DNS_NS、DNS_PTR、DNS_SOA、DNS_TXT、DNS_AAAA、DNS_SRV、DNS_NAPTR、DNS_A6、DNS_ALL 或 DNS_ANY。

注意:
因为不同平台间的 libresolv 存在性能差异，DNS_ANY 不会始终返回每条记录，较慢的 DNS_ALL 会更可靠的收集所有记录。

注意:
Windows：不支持 DNS_CAA。没有实现对 DNS_A6 的支持。
authoritative_name_servers: 引用传递，如果给出，将会填充权威名称服务器的资源记录。
additional_records: 引用传递，如果给出，将会填充任何附加记录。
raw: type 将解释为原始 DNS 类型 ID（不能使用 DNS_* 常量）。返回值包含 data 键，需要手动解析。

返回值

此函数返回由关联数组组成的数组，或者在失败时返回 false。每个关联数组至少包含以下键：

**基础 DNS 属性**
属性	含义
host	The record in the DNS namespace to which the rest of the associated data refers.
class	dns_get_record() 仅返回内部类记录，因此参数将始终返回 `IN`。
type	包含记录类型的字符串。其他属性也包含在结果数组中，具体取决于 type 的值。查看下表。
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.

**根据“type”的不同，出现的关联数组的其它键**
类型	额外列
`A`	`ip`：点分十进制格式的 IPv4。
`MX`	`pri`：邮件交换器的有优先级。较低的数字有较高的优先级。`target`：邮件服务器的 FQDN（全称域名）。参阅 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`：跟此记录关联的任意字符串数据。
`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.
`CAA`	`flags`：单字节位字段；目前仅定义了第 0 位，意味着“critical”；其他位保留且应该忽略。`tag`：CAA 标记名（字母数字的 ASCII 字符串）。`value`：CAA 标记值（二进制字符串，可以使用子格式）。更多信息参阅：» RFC 6844。
`SOA`	`mname`: FQDN of the machine from which the resource records originated. `rname`: Email address of the administrative contact 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 地址
`A6`	`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.

更新日志

版本	说明
7.0.16, 7.1.2	新增对 CAA 记录的支持。

示例

示例 #1 使用 dns_get_record()

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

以上示例的输出类似于：

 
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() 和 DNS_ANY

一旦解析了 MX 记录，通常需要邮件服务器的 IP 地址，因此 dns_get_record() 还会在 additional_records 中返回包含关联记录的数组。authoritative_name_servers 也会返回，包含权威名称服务器列表。

<?php
/* 为 php.net 请求“ANY”记录，并创建 $authns 和 $addtl 数组，
   包含名称服务器列表和任何附加记录列表 */
$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);
?>

以上示例的输出类似于：

参见

dns_get_mx() - 别名 getmxrr
dns_check_record() - 别名 checkdnsrr

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User Contributed Notes 9 notes

down

tobias at herkula dot info ¶

8 years ago

This method has no error handling, it simply puts out "false" and it is impossible to check for NXDOMAIN, SERVFAIL, TIMEOUT or any other error...

down

NaturalBornCamper ¶

6 years ago

You might have the same problem as me, where testing a non-existent domain will search for a subdomain relative to the domain you are executing from, for example:

// Test with working domain
var_dump( dns_get_record('google.com', DNS_A) );
/* works, returns
Array
(
    [host] => google.com
    [class] => IN
    [ttl] => 299
    [type] => A
    [ip] => 172.217.12.142
)
*/

// Test with invalid domain on our website (example.com)
var_dump( dns_get_record('invalidtestingname.com', DNS_A) );
/* Doesn't work, pretend it's a subdomain
Array
(
    [host] => invalidtestingname.com.example.com
    [class] => IN
    [ttl] => 299
    [type] => A
    [ip] => xxx.xxx.xxx.xxx
)
*/

If anyone has that problem, add a "dot" at the end of the domain name, for example, instead of
dns_get_record('invalidtestingname.com', DNS_A);
Do this:
dns_get_record('invalidtestingname.com.', DNS_A);

down

dylan at pow7 dot com ¶

14 years ago

Get more than one type at once like this:
<?php
$dnsr = dns_get_record('php.net', DNS_A + DNS_NS);
print_r($dnsr);
?>

Using DNS_ALL fails on some domains where DNS_ANY works. I noticed the function getting stuck on the DNS_PTR record, which caused it to return FALSE with this error:
PHP Warning:  dns_get_record(): res_nsend() failed in ....

This gets all records except DNS_PTR:
<?php
$dnsr = dns_get_record('php.net', DNS_ALL - DNS_PTR);
print_r($dnsr);
?>

down

PHP Joe ¶

10 years ago

Although this works very well for general DNS queries if you want to do a direct DNS query to a specified DNS server (rather than using OS resolution) try PHPDNS: http://www.purplepixie.org/phpdns/

You can do direct (TCP or UDP) low-level queries to a nameserver and recurse at will. Very useful for testing specific servers and also for walking through a recursive resolution.

down

heinjan at eendrachtstraat dot nl ¶

7 years ago

Please note that Firewalls and anti malware software detects  (and depending on company policies even blocks) DNS_ANY requests. 
In that case the usage of this function fails.
This is because DNS_ANY requests can be  exploited for creating "amplification (D)DOS attackes": You send 1 DNS_ANY request and get a huge amount of information back, thus even small requests can result into hugh network load.

I advise to use a more explicit name-request instead of using DNS_ANY.

down

ohcc at 163 dot com ¶

6 years ago

When I use DNS_ALL as the second parameter to invoke dns_get_record() on the OS of Windows, PHP emits a warning with the message "Warning: dns_get_record(): Type '251721779' not supported in blah.php on line blah", and DNS_ANY is always OKAY.

down

bohwaz ¶

1 year ago

Sadly this method does not allow for using an arbitrary nameserver.

If you need to make a request  using a specific DNS server, you'll need to use either Pear/Net_DNS2, or libdns ( https://github.com/DaveRandom/LibDNS ).

If you want something shorter and lighter, you can also use this 150 lines function: https://gist.github.com/bohwaz/ddc61c4f7e031c3221a89981e70b830c

down

-9

karl at influ dot io ¶

10 years ago

There's a comment below from 7 years ago regarding BSD and MacOSX, I'd just like to follow up incase some people see that and don't think it'll work on MacOSX.

Software:

    System Software Overview:

      System Version: OS X 10.8.3 (12D78)
      Kernel Version: Darwin 12.3.0
      Boot Volume: Macintosh HD
      Boot Mode: Normal
      Computer Name: Karl’s iMac
      User Name: Karl Kloppenborg (karl)
      Secure Virtual Memory: Enabled
      Time since boot: 10 days 20:24
--------------

# php -a
php > print_r(dns_get_record('google.com', DNS_MX));

Array
(
    [0] => Array
        (
            [host] => google.com
            [type] => MX
            [pri] => 10
            [target] => aspmx.l.google.com
            [class] => IN
            [ttl] => 749
        )

    [1] => Array
        (
            [host] => google.com
            [type] => MX
            [pri] => 30
            [target] => alt2.aspmx.l.google.com
            [class] => IN
            [ttl] => 749
        )

    [2] => Array
        (
            [host] => google.com
            [type] => MX
            [pri] => 50
            [target] => alt4.aspmx.l.google.com
            [class] => IN
            [ttl] => 749
        )

    [3] => Array
        (
            [host] => google.com
            [type] => MX
            [pri] => 40
            [target] => alt3.aspmx.l.google.com
            [class] => IN
            [ttl] => 749
        )

    [4] => Array
        (
            [host] => google.com
            [type] => MX
            [pri] => 20
            [target] => alt1.aspmx.l.google.com
            [class] => IN
            [ttl] => 749
        )

)

down

-17

Emil ¶

5 years ago

Hi,
If I added domain to directadmin where is script with dns_get_record it gives me local values even if that domain is not really delegated yet to this server.. why?

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