dns_get_record()

(PHP 5, PHP 7)

获取指定主机的DNS记录

说明

获取指定主机（$hostname）的DNS记录。

参数

主机名（$hostname）应该是一个DNS解析生效的域名，例如“www.example.com”。主机名也可以是通过对逆向解析域做DNS逆向域名解析而得到，但是在大多数情况下gethostbyaddr()更加适合做逆向域名解析。

每个DNS标准，邮件地址必须是user.host这样的格式（例如hostmaster.example.com而不是hostmaster@example.com），在使用mail()这个函数之前请检查这个值，有必要的话还需要修改。$type

默认情况下，dns_get_record()将会搜索所有与$hostname相关的记录，可以通过设置$type来限定查询。$type的值可以是下面的其中的任何一个：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。

由于dns在各个平台上表现有些不一样，DNS_ANY不会总是返回所有的记录，DNS_ALL虽然慢一些，但是会得到所有的记录，所以使用DNS_ALL更加可靠些。$authns

以引用方式传递，如果写了该参数，那么将会得到该解析记录的DNS服务器（Authoritative Name Servers）的信息。

以引用方式传递，如果填写了该参数，将会得到其他所有的DNS解析记录。

在原生模式下，在进行额外的查询的时候之前我们只执行请求的DNS类型，而不是循环查询所有的类型。

返回值

这个函数返回一个关联数组，如果失败则或者在失败时返回FALSE。每个关联数组都至少包含了以下的这些键。at minimumthe following keys:

更新日志

范例

使用dns_get_record()函数

以上例程的输出类似于：

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
        )
)

使用dns_get_record()配合DNS_ANY的例子

由于我们经常会想获取一个邮件服务器的对应的IP地址的MX记录是否已经生效。在使用dns_get_record()函数之后，$addtl能够返回一个相关的数组记录，$authns参数则会返回授权服务器的列表信息。

以上例程的输出类似于：

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
        )
)

注释

For compatibility with versions before PHP 5.3.0 on some operating systems, try the» PEARclass» Net_DNS.

参见

• dns_get_mx() 别名 getmxrr
• dns_check_record() 别名 checkdnsrr

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...

Get more than one type at once like this:

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: 

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.

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);

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.

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.

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?

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
    )
)

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