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<refentry xml:id="function.dns-get-record" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
 <refnamediv>
  <refname>dns_get_record</refname>
  <refpurpose>Fetch DNS Resource Records associated with a hostname</refpurpose>
 </refnamediv>
 
 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type class="union"><type>array</type><type>false</type></type><methodname>dns_get_record</methodname>
   <methodparam><type>string</type><parameter>hostname</parameter></methodparam>
   <methodparam choice="opt"><type>int</type><parameter>type</parameter><initializer><constant>DNS_ANY</constant></initializer></methodparam>
   <methodparam choice="opt"><type>array</type><parameter role="reference">authoritative_name_servers</parameter><initializer>&null;</initializer></methodparam>
   <methodparam choice="opt"><type>array</type><parameter role="reference">additional_records</parameter><initializer>&null;</initializer></methodparam>
   <methodparam choice="opt"><type>bool</type><parameter>raw</parameter><initializer>&false;</initializer></methodparam>
  </methodsynopsis>
  <para>
   Fetch DNS Resource Records associated with the given
   <parameter>hostname</parameter>.
  </para>
 </refsect1>

 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>hostname</parameter></term>
     <listitem>
      <para>
       <parameter>hostname</parameter> should be a valid DNS hostname such
       as "<literal>www.example.com</literal>". Reverse lookups can be generated
       using <literal>in-addr.arpa</literal> notation, but
       <function>gethostbyaddr</function> is more suitable for
       the majority of reverse lookups.
      </para>
      <note>
       <para>
        Per DNS standards, email addresses are given in <literal>user.host</literal> format (for
        example: <literal>hostmaster.example.com</literal> as opposed to <literal>hostmaster@example.com</literal>),
        be sure to check this value and modify if necessary before using it
        with a functions such as <function>mail</function>.
       </para>
      </note>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>type</parameter></term>
     <listitem>
      <para>
       By default, <function>dns_get_record</function> will search for any
       resource records associated with <parameter>hostname</parameter>. 
       To limit the query, specify the optional <parameter>type</parameter>
       parameter. May be any one of the following:
       <constant>DNS_A</constant>, <constant>DNS_CNAME</constant>,
       <constant>DNS_HINFO</constant>, <constant>DNS_CAA</constant>,
       <constant>DNS_MX</constant>, <constant>DNS_NS</constant>,
       <constant>DNS_PTR</constant>, <constant>DNS_SOA</constant>,
       <constant>DNS_TXT</constant>, <constant>DNS_AAAA</constant>,
       <constant>DNS_SRV</constant>, <constant>DNS_NAPTR</constant>,
       <constant>DNS_A6</constant>, <constant>DNS_ALL</constant>
       or <constant>DNS_ANY</constant>.
      </para>
      <note>
       <para>
        Because of eccentricities in the performance of libresolv
        between platforms, <constant>DNS_ANY</constant> will not
        always return every record, the slower <constant>DNS_ALL</constant>
        will collect all records more reliably.
       </para>
      </note>
      <note>
       <para>
        Windows: <constant>DNS_CAA</constant> is not supported.
        Support for <constant>DNS_A6</constant> is not implemented.
       </para>
      </note>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>authoritative_name_servers</parameter></term>
     <listitem>
      <para>
       Passed by reference and, if given, will be populated with Resource
       Records for the <emphasis>Authoritative Name Servers</emphasis>.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>additional_records</parameter></term>
     <listitem>
      <para>
       Passed by reference and, if given, will be populated with any
       <emphasis>Additional Records</emphasis>.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>raw</parameter></term>
     <listitem>
      <para>
       The <parameter>type</parameter> will be interpreted as a raw DNS type ID
       (the <literal>DNS_*</literal> constants cannot be used).
       The return value will contain a <literal>data</literal> key, which needs
       to be manually parsed.
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>

 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   This function returns an array of associative arrays,
   &return.falseforfailure;. Each associative array contains
   <emphasis>at minimum</emphasis> the following keys:
   <table>
    <title>Basic DNS attributes</title>
    <tgroup cols="2">
     <thead>
      <row>
       <entry>Attribute</entry>
       <entry>Meaning</entry>
      </row>
     </thead>
     <tbody>
      <row>
       <entry>host</entry>
       <entry>
        The record in the DNS namespace to which the rest of the associated data refers.
       </entry>
      </row>
      <row>
       <entry>class</entry>
       <entry>
        <function>dns_get_record</function> only returns Internet class records and as
        such this parameter will always return <literal>IN</literal>.
       </entry>
      </row>
      <row>
       <entry>type</entry>
       <entry>
        String containing the record type.  Additional attributes will also be contained
        in the resulting array dependant on the value of type. See table below.
       </entry>
      </row>
      <row>
       <entry>ttl</entry>
       <entry>
        <literal>"Time To Live"</literal> remaining for this record. This will <emphasis>not</emphasis> 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.
       </entry>
      </row>
     </tbody>
    </tgroup>
   </table>
  </para>
  <para>
   <table>
    <title>Other keys in associative arrays dependant on 'type'</title>
    <tgroup cols="2">
     <thead>
      <row>
       <entry>Type</entry>
       <entry>Extra Columns</entry>
      </row>
     </thead>
     <tbody>
      <row>
       <entry><literal>A</literal></entry>
       <entry>
        <literal>ip</literal>: An IPv4 addresses in dotted decimal notation.
       </entry>
      </row>
      <row>
       <entry><literal>MX</literal></entry>
       <entry>
        <literal>pri</literal>: Priority of mail exchanger.
        Lower numbers indicate greater priority.
        <literal>target</literal>: FQDN of the mail exchanger.
        See also <function>dns_get_mx</function>.
       </entry>
      </row>
      <row>
       <entry><literal>CNAME</literal></entry>
       <entry>
        <literal>target</literal>: FQDN of location in DNS namespace to which
        the record is aliased.
       </entry>
      </row>
      <row>
       <entry><literal>NS</literal></entry>
       <entry>
        <literal>target</literal>: FQDN of the name server which is authoritative
        for this hostname.
       </entry>
      </row>
      <row>
       <entry><literal>PTR</literal></entry>
       <entry>
        <literal>target</literal>: Location within the DNS namespace to which
        this record points.
       </entry>
      </row>
       <row>
       <entry><literal>TXT</literal></entry>
       <entry>
        <literal>txt</literal>: Arbitrary string data associated with this record.
       </entry>
      </row>
      <row>
       <entry><literal>HINFO</literal></entry>
       <entry>
        <literal>cpu</literal>: IANA number designating the CPU of the machine
        referenced by this record.
        <literal>os</literal>: IANA number designating the Operating System on
        the machine referenced by this record.
        See IANA's <link xlink:href="&url.iana.system-names;"><literal>Operating System
        Names</literal></link> for the meaning of these values.
       </entry>
      </row>
      <row>
       <entry><literal>CAA</literal></entry>
       <entry>
        <literal>flags</literal>: A one-byte bitfield; currently only bit 0 is defined,
        meaning 'critical'; other bits are reserved and should be ignored.
        <literal>tag</literal>: The CAA tag name (alphanumeric ASCII string).
        <literal>value</literal>: The CAA tag value (binary string, may use subformats).
        For additional information see: <link xlink:href="&url.rfc;6844">RFC 6844</link>
       </entry>
      </row>
      <row>
       <entry><literal>SOA</literal></entry>
       <entry>
        <literal>mname</literal>: FQDN of the machine from which the resource
        records originated.
        <literal>rname</literal>: Email address of the administrative contact
        for this domain.
        <literal>serial</literal>: Serial # of this revision of the requested
        domain.
        <literal>refresh</literal>: Refresh interval (seconds) secondary name
        servers should use when updating remote copies of this domain.
        <literal>retry</literal>: Length of time (seconds) to wait after a
        failed refresh before making a second attempt.
        <literal>expire</literal>: Maximum length of time (seconds) a secondary
        DNS server should retain remote copies of the zone data without a
        successful refresh before discarding.
        <literal>minimum-ttl</literal>: 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.
       </entry>
      </row>
      <row>
       <entry><literal>AAAA</literal></entry>
       <entry>
        <literal>ipv6</literal>: IPv6 address
       </entry>
      </row>
      <row>
       <entry><literal>A6</literal></entry>
       <entry>
        <literal>masklen</literal>: Length (in bits) to inherit from the target
        specified by <parameter>chain</parameter>.
        <literal>ipv6</literal>: Address for this specific record to merge with
        <parameter>chain</parameter>.
        <literal>chain</literal>: Parent record to merge with
        <parameter>ipv6</parameter> data.
       </entry>
      </row>
      <row>
       <entry><literal>SRV</literal></entry>
       <entry>
        <literal>pri</literal>: (Priority) lowest priorities should be used first.
        <literal>weight</literal>: Ranking to weight which of commonly prioritized
        <parameter>targets</parameter> should be chosen at random.
        <literal>target</literal> and <literal>port</literal>: hostname and port
        where the requested service can be found.
        For additional information see: <link xlink:href="&url.rfc;2782">RFC 2782</link>
       </entry>
      </row>
      <row>
       <entry><literal>NAPTR</literal></entry>
       <entry>
        <literal>order</literal> and <literal>pref</literal>: Equivalent to
        <parameter>pri</parameter> and <parameter>weight</parameter> above.
        <literal>flags</literal>, <literal>services</literal>, <literal>regex</literal>,
        and <literal>replacement</literal>: Parameters as defined by
        <link xlink:href="&url.rfc;2915">RFC 2915</link>.
       </entry>
      </row>
     </tbody>
    </tgroup>
   </table>
  </para>
 </refsect1>

 <refsect1 role="changelog">
  &reftitle.changelog;
  <para>
   <informaltable>
    <tgroup cols="2">
     <thead>
      <row>
       <entry>&Version;</entry>
       <entry>&Description;</entry>
      </row>
     </thead>
     <tbody>
      <row>
       <entry>7.0.16, 7.1.2</entry>
       <entry>
        Added support for CAA record type.
       </entry>
      </row>
     </tbody>
    </tgroup>
   </informaltable>
  </para>
 </refsect1>

 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title>Using <function>dns_get_record</function></title>
    <programlisting role="php">
<![CDATA[
<?php
$result = dns_get_record("php.net");
print_r($result);
?>
]]>
    </programlisting>
    &example.outputs.similar;
    <screen>
<![CDATA[
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
        )

)
]]>
    </screen>
   </example>
   <example>
    <title>Using <function>dns_get_record</function> and DNS_ANY</title>
    <para>
     Since it's very common to want the IP address of a mail server
     once the MX record has been resolved, <function>dns_get_record</function>
     also returns an array in <parameter>additional_records</parameter> which
     contains associate records.  <parameter>authoritative_name_servers</parameter>
     is returned as well containing a list of authoritative name
     servers.
    </para>
    <programlisting role="php">
<![CDATA[
<?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);
?>
]]>
    </programlisting>
    &example.outputs.similar;
    <screen>
<![CDATA[
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
        )

)
]]>
    </screen>
   </example>
  </para>
 </refsect1>

 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><function>dns_get_mx</function></member>
    <member><function>dns_check_record</function></member>
   </simplelist>
  </para>
 </refsect1>

</refentry>
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