### BIND TSIG Configuration Example

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Example BIND configuration for a zone allowing updates using a TSIG key. This setup is required on the DNS server to enable TSIG authentication.

```BIND Configuration
key "mykey" {
    algorithm hmac-sha256;
    secret "9dnf93asdf39fs";
};

zone "example.com" {
    type master;
    file "dynamic/example.com";

    allow-transfer {
        key "mykey";
    }

    allow-update {
        key "mykey";
    };
};
```

--------------------------------

### Install NetDNS2 using Composer

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Use Composer to add the NetDNS2 library to your PHP project. This is the recommended installation method.

```bash
composer require mikepultz/netdns2
```

--------------------------------

### NetDNS2 Resolver Configuration Example

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Demonstrates how to configure the NetDNS2 Resolver with various options such as name servers, timeouts, TCP/TLS usage, and caching. These options can be passed to the constructor.

```php
$r = new \NetDNS2\Resolver([
    // an array of IP addresses to use as name servers. If this is unset it will 
    // default to using the /etc/resolv.conf file.
    // array, defaults to unset.
    'nameservers'   => [ '1.1.1.1', '8.8.8.8' ],

    // tells NetDNS2 to randomize the name servers list each time it’s used.
    // boolean, defaults to false
    'ns_random'     => true,

    // timeout value to use for socket connections, provided as float, with microsecond 
    // precision. e.g. a value of 1.0 will timeout in 1 second. A value of 0.05 will 
    // timeout in 50 milliseconds.
    // float, defaults to 5 seconds
    'timeout'       => 0.05,

    // tells NetDNS2 to use TCP instead of UDP for queries. UDP is faster, but is limited 
    // in size. NetDNS2 will automatically use TCP for zone transfers (AFXR) and when 
    // a response was truncated.
    // in the event of a truncated response, NetDNS2 will switch to TCP, and resend the 
    // request.
    // boolean, defaults to false.
    'use_tcp'       => true,

    // use DNS over TLS (DoT) this requires OpenSSL support enabled in PHP
    // enabling this option will also enable use_tcp, and sets the default port to 853
    // boolean, defaults to false.
    'use_tls'       => true,

    // if set, these values are passed to stream_context_create() as the 'ssl' transport 
    // section, which lets you customize TLS connection settings.
    // only applies when use_tls = true
    // array, defaults to empty
    'tls_context'   => [ 'verify_peer' => false, 'verify_peer_name' => false ],

    // DNS Port to use; -1 means default of 53 (or 853 when using DoT)
    // int, defaults to -1
    'dns_port'      => 53,

    // the local IP address to bind to when making outbound requests.
    // string, defaults to unset.
    'local_host'    => '',

    // the local port number to bind to when making outbound requests. local_host can be 
    // set without this setting, and the system will auto-allocate the port from the 
    // ephemeral ports.
    // int, defaults to 0 (unset)
    'local_port'    => 0,

    // The default domain to use for unqualified host names.
    // string, defaults to unset
    'domain'        => 'netdns2.com',

    // defines the type of cache to use, using a pre-defined ENUM option. valid options 
    // are:
    //  \NetDNS2\Cache::CACHE_TYPE_NONE         - disables the local cache
    //  \NetDNS2\Cache::CACHE_TYPE_FILE         - flat file cache
    //  \NetDNS2\Cache::CACHE_TYPE_SHM          - shared memory (requires Shmop extension)
    //  \NetDNS2\Cache::CACHE_TYPE_MEMCACHED    - memcache (requires Memcached extension)
    //  \NetDNS2\Cache::CACHE_TYPE_REDIS        - redis (requires Redis extension)
    // int, defaults to \NetDNS2\Cache::CACHE_TYPE_NONE
    'cache_type'    => \NetDNS2\Cache::CACHE_TYPE_MEMCACHED,

    // options to pass to the underlying caching objects
    // array, defaults to empty
    'cache_options' => [
        'server' => [
            [ '127.0.0.1', 11211 ]
        ],
        'options' => [
            \Memcached::OPT_COMPRESSION => true
        ]
    ],

    // strict_query_mode means that if the hostname that was looked up isn’t actually in 
    // the answer section of the response, NetDNS2 will return an empty answer section, 
    // instead of an answer section that could contain CNAME records.
    // boolean, defaults to false
    'strict_query_mode' => true,

    // if we should set the recursion desired bit to 1 or 0.
    // by default this is set to true, we want the DNS server to perform a recursive 
    // request. If set to false, the RD bit will be set to 0, and the server will not 
    // perform recursion on the request.
    // boolean, defaults to true
    'recurse'   => true,

    // request DNSSEC values, by setting the DO flag to 1
    // this instructs the upstream resolvers that we want to include DNSSEC details
]
```

--------------------------------

### Setting Resolver Properties

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Configuration options can be set as properties on the Resolver object after initialization. This example shows how to set the timeout and DNSSEC option.

```php
$r = new 

    $r->timeout = 1.5;
    $r->dnssec = true;

    $res = $r->query('google.com', 'A');
```

--------------------------------

### Perform Zone Transfer (AXFR)

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

This example demonstrates how to perform a zone transfer (AXFR) for a domain. It includes setting up a resolver with a specific nameserver and signing the request with TSIG.

```php
try
    {
        //
        // create new resolver object, passing in an array of name servers to use for lookups
        //
        $r = new \NetDNS2\Resolver([ 'nameservers' => [ '192.168.0.1' ]]);

        //
        // add a TSIG to authenticate the request
        //
        $r->signTSIG('mykey', '9dnf93asdf39fs');

        //
        // execute the zone transfer request for example.com
        //
        $res = $r->query('example.com', 'AXFR');

        //
        // loop through the answer, printing out each resource record.
        //
        foreach($res->answer as $rr)
        {
            print_r($rr);
        }

    } catch(\\NetDNS2\\Exception $e)
    {
        echo "::query() failed: ", $e->getMessage(), "\n";
    }
```

--------------------------------

### Enable Multiple EDNS Options

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

This example shows how to enable multiple EDNS options, including client subnet, TCP keepalive, and NSID, in a single DNS query. Ensure that 'use_tcp' is set to true when using tcp_keepalive.

```php
//
// create a new Resolver object
//
$r = new \NetDNS2\Resolver([ 'nameservers' => [ '192.168.0.1' ]]);

//
// enable the client subnet option, and pass in my IP range
//
$r->edns->client_subnet(true, '10.10.10.0/24');

//
// set a TCP keepalive value
//
$r->edns->tcp_keepalive(true, 300);

//
// request name server identifier information
//
$r->edns->nsid(true);

//
// request the A record
//
$res = $r->query('example.com', 'A');
```

--------------------------------

### Configure TLS Context for DoT

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

This example demonstrates how to configure TLS-specific options for DoT, such as disabling peer verification, by setting the 'tls_context' array. These options are passed to stream_context_create().

```php
$r->use_tls = true;

    $r->tls_context = [ 'verify_peer' => false, 'verify_peer_name' => false ];
```

--------------------------------

### Get MX Records

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

This snippet retrieves Mail Exchanger (MX) records for a domain. It iterates through the results to display preference and host information.

```php
try
    {
        //
        // create new resolver object, passing in an array of name servers to use for lookups
        //
        $r = new \NetDNS2\Resolver(['nameservers' => [ '1.1.1.1' ]]);

        //
        // execute the query request for the google.com MX servers
        //
        $res = $r->query('google.com', 'MX');

        //
        // loop through the answer, printing out the MX servers returned.
        //
        foreach($res->answer as $mxrr)
        {
            printf("preference=%d, host=%s\n", $mxrr->preference, $mxrr->exchange);
        }

    } catch(\\NetDNS2\\Exception $e)
    {
        echo "::query() failed: " . $e->getMessage() . "\n";
    }
```

--------------------------------

### Create DNS Notifier Object

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Initialize a NetDNS2 Notifier object for a domain and its authoritative nameservers.

```php
$n = new \NetDNS2\Notifier('netdns2.com', ['nameservers' => [ '192.168.0.1' ]]);
```

--------------------------------

### Enable DNS over HTTP (DoH)

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Configure the NetDNS2 Resolver to use DoH servers by passing their URLs in the 'nameservers' array. Requires the cURL extension.

```php
try
{
    //
    // create new resolver object, passing in an array of DoH servers
    //
    $r = new \NetDNS2\Resolver(['nameservers' => [ 'https://cloudflare-dns.com/dns-query' ]]);

    //
    // execute the query request for the facebook A record
    //
    $res = $r->query('facebook.com', 'A');

    //
    // if facebook points to more than one IP, then you can loop through the answer array to
    // see each IP address.
    //
    echo "facebook resolves to: " . $res->answer[0]->address;

} catch(\
```

```php
\NetDNS2\Exception $e
{
    echo "::query() failed: " . $e->getMessage() . "\n";
}

```

--------------------------------

### Perform A Record Lookup

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Use this snippet to perform a simple A record lookup for a given domain. It requires creating a Resolver instance and specifying the nameservers.

```php
try
    {
        //
        // create new resolver object, passing in an array of name servers to use for lookups
        //
        $r = new \NetDNS2\Resolver(['nameservers' => [ '1.1.1.1' ]]);

        //
        // execute the query
        //
        $res = $r->query('facebook.com', 'A');

        //
        // if facebook points to more than one IP, then you can loop through the answer array to
        // see each IP address.
        //
        echo "facebook resolves to: " . $res->answer[0]->address;

    } catch(\\NetDNS2\\Exception $e)
    {
        echo "::query() failed: " . $e->getMessage() . "\n";
    }
```

--------------------------------

### Upgrade from NetDNS2 v1.x to v2.x

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Illustrates the namespace changes required when upgrading from NetDNS2 version 1.x to 2.x. The underlying class and function names remain largely the same.

```php
v1.x

    try  
    {
        $r = new Net_DNS2_Resolver([ 'nameservers' => [ '192.168.0.1' ]]);

        $res = $r->query('google.com', 'MX');

    } catch(Net_DNS2_Exception $e)
    {
        print_r($e);
    }


v2.x

    try   
    {
        $r = new \NetDNS2\Resolver([ 'nameservers' => [ '192.168.0.1' ]]);

        $res = $r->query('google.com', 'MX');

    } catch(\NetDNS2\Exception $e)  
    {
        print_r($e);
    }
```

--------------------------------

### Create DNS Updater Object

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Initialize a NetDNS2 Updater object for a specific domain and its authoritative nameservers.

```php
$u = new \NetDNS2\Updater('example.com', [ 'nameservers' => [ '192.168.0.1' ]]);
```

--------------------------------

### NetDNS2 TSIG Authentication for Updates

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Demonstrates how to create a NetDNS2 Updater object and sign outgoing dynamic DNS update requests using TSIG authentication. Ensure the key name and secret match the BIND configuration.

```PHP
$u = new \NetDNS2\Updater('example.com', [ 'nameservers' => [ '192.168.0.1' ]]);

//
// add a TSIG to authenticate the request
//
$u->signTSIG('mykey', '9dnf93asdf39fs');

//
// send the update request.
//
$u->update();
```

--------------------------------

### Configure Redis Cache

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Instantiate a NetDNS2 Resolver with Redis caching enabled. Specify host and port for the Redis server.

```php
$r = new \NetDNS2\Resolver([
        'nameservers'   => [ '192.168.0.1' ]

        'cache_type'    => \NetDNS2\Cache::CACHE_TYPE_REDIS,
        'cache_options' => [

            'host' => '127.0.0.1',
            'port' => 6379
        ]
    ]);
```

--------------------------------

### Configure Memcached Cache

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Instantiate a NetDNS2 Resolver with Memcached caching enabled. Specify server details and Memcached options.

```php
$r = new \NetDNS2\Resolver([
        'nameservers'   => [ '192.168.0.1' ]

        'cache_type'    => \NetDNS2\Cache::CACHE_TYPE_MEMCACHED,
        'cache_options' => [

            'server' => [

                [ '127.0.0.1', 11211 ]
            ],
            'options' => [

                \Memcached::OPT_COMPRESSION => true
            ]
        ]
    ]);
```

--------------------------------

### Configuring Flat File Cache

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Creates a NetDNS2 Resolver with a flat file cache enabled. Specifies the cache file path, maximum size, and an optional TTL override.

```php
$r = new \\NetDNS2\\Resolver(
    [
        'nameservers'   => [ '192.168.0.1' ]

        'cache_type'    => \\NetDNS2\\Cache::CACHE_TYPE_FILE,
        'cache_options' => [

            'file'  => '/tmp/cache.txt',    // the file to serialize cache content to
            'size'  => 50000,               // the max file size for this cache file

            'ttl_override' => 300           // int, in seconds, to cache data for
        ]
    ]
);
```

--------------------------------

### Configuring Shared Memory (Shm) Cache

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Initializes a NetDNS2 Resolver using the Shmop extension for shared memory caching. Configures the cache file (used for IPC key), segment size, and an optional project ID for the ftok() function.

```php
$r = new \\NetDNS2\\Resolver(
    [
        'nameservers'   => [ '192.168.0.1' ]

        'cache_type'    => \\NetDNS2\\Cache::CACHE_TYPE_SHM,
        'cache_options' => [

            'file'  => '/tmp/cache.txt',    // the file to use as the System V IPC key (via ftok())
            'size'  => 50000,               // the max shared memory segment size in bytes
            'id'    => 't'                  // ftok() project ID; change to use multiple independent segments
        ]
    ]
);
```

--------------------------------

### Configuring IPv6 DNS Server

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Initializes a NetDNS2 Resolver to use IPv6 DNS servers. This can be set directly in the nameservers array.

```php
$r = new \\NetDNS2\\Resolver([ 'nameservers' => [ '::1' ]]);
```

--------------------------------

### NetDNS2 SIG(0) Authentication for Updates

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Shows how to sign dynamic DNS update requests using SIG(0) authentication with NetDNS2. This requires the path to a private key file generated by dnssec-keygen and the OpenSSL extension to be enabled in PHP.

```PHP
$u = new \NetDNS2\Updater('example.com', [ 'nameservers' => [ '192.168.0.1' ]]);

//
// add a SIG(0) to authenticate the request; this is the path to the private key file
//
$u->signSIG0('/etc/named/Kexample.com.+001+15765.private');

//
// send the update request.
//
$u->update();
```

--------------------------------

### Enable DNS over TLS (DoT)

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

This snippet shows how to enable DNS over TLS (DoT) by setting the 'use_tls' option to true. This requires the OpenSSL extension and changes the default port to 853, using TCP.

```php
try
    {
        //
        // create new resolver object, passing in an array of name servers to use for lookups
        //
        $r = new \NetDNS2\Resolver(['nameservers' => [ '1.1.1.1' ]]);

        //
        // enable DoT
        //
        $r->use_tls = true;

        //
        // execute the query request for the google.com MX servers
        //
        $res = $r->query('facebook.com', 'A');

        //
        // if facebook points to more than one IP, then you can loop through the answer array to
        // see each IP address.
        //
        echo "facebook resolves to: " . $res->answer[0]->address;

    } catch(\\NetDNS2\\Exception $e)
    {
        echo "::query() failed: " . $e->getMessage() . "\n";
    }
```

--------------------------------

### Enable Update Lease EDNS Option

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Use this snippet to enable the 'update_lease' EDNS option, specifying a desired lease time. This option is related to DNSSEC and lease management.

```php
//
// update_lease(boolean enable, int desired_lease_time, int desired_key_lease_time = 0)
//
$u->edns->update_lease(true, time());
```

--------------------------------

### Sign DNS Notify Request with TSIG

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Add a TSIG key and secret to authenticate the DNS notify request.

```php
$n->signTSIG('mykey', '9dnf93asdf39fs');
```

--------------------------------

### Enable Key Tag EDNS Option

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

This snippet shows how to enable the Key Tag EDNS option, providing a list of key tags as defined in RFC 8145.

```php
//
// key_tag(boolean enable, array list_of_key_tags)
//
$r->edns->key_tag(true, [ 12345, 67890 ]);
```

--------------------------------

### Specify NetDNS2 v1.x in Composer

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Configure your composer.json file to pin the NetDNS2 dependency to version 1.x if you need to maintain compatibility with older projects.

```json
{
    "require": {
        "mikepultz/netdns2": "^1.5"
    }
}
```

--------------------------------

### Send DNS Update Request

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Execute all pending DNS update commands queued in the Updater object.

```php
$u->update();
```

--------------------------------

### Performing IPv6 Forward DNS Lookup (AAAA Record)

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Performs a forward DNS lookup for an IPv6 address, retrieving the AAAA record.

```php
$res = $r->query('a2.test.com', 'AAAA');

a2.test.com. 86400 IN AAAA ff01:0:0:0:0:0:0:43
```

--------------------------------

### Enable Client Subnet EDNS Option with IPv6 Address

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

This snippet demonstrates enabling the client subnet EDNS option using an IPv6 address or subnet, as specified in RFC 7871. It allows for more granular control over client IP information.

```php
//
// client_subnet(boolean enable, string address)
//
$r->edns->client_subnet(true, '2607:f8b0:4009:81a::200e/56');
```

--------------------------------

### Add Resource Record for Notify

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Add a resource record to the Notifier object, which will trigger a notify against secondary servers.

```php
$n->add(\NetDNS2\RR::fromString('test.netdns2.com 600 IN A 2.2.2.2'));
```

--------------------------------

### Enable Chain EDNS Option

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Use this snippet to enable the 'chain' EDNS option, providing the FQDN of the closest trust point, as defined in RFC 7901.

```php
//
// chain(boolean enable, string fqdn_of_closest_trust_point)
//
$r->edns->chain(true, 'com.');
```

--------------------------------

### Enable DNSSEC Verification

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Set the 'dnssec' flag to true on the Resolver object to request DNSSEC records and verification. The 'ad' bit in the response header indicates success.

```php
try
{
    //
    // create new resolver object, passing in an array of name servers to use for lookups
    //
    $r = new \NetDNS2\Resolver(['nameservers' => [ '1.1.1.1' ]]);

    //
    // request DNSSEC records
    //
    $r->dnssec = true;

    //
    // execute the query
    //
    $res = $r->query('org', 'SOA');

    //
    // check the ad flag; if it's set to 1, then the upstream resolver is confirming that
    // the DNSSEC verification was successful and we can trust the results.
    //
    if ($res->header->ad == 1)
    {
        echo "DNSSEC verification success!";
    } else
    {
        echo "DNSSEC verification failure; we can't trust this response.";
    }

} catch(\
```

```php
\NetDNS2\Exception $e
{
    echo "::query() failed: " . $e->getMessage() . "\n";
}

```

--------------------------------

### Enable Client Subnet EDNS Option

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Use this snippet to include the client subnet option in a DNS query as per RFC 7871. It requires creating a Resolver and then enabling the client_subnet option with a specified IP range.

```php
//
// create a new Resolver object
//
$r = new \NetDNS2\Resolver([ 'nameservers' => [ '192.168.0.1' ]]);

//
// enable the client subnet option, and pass in my IP range
//
$r->edns->client_subnet(true, '10.10.10.0/24');

//
// request the A record
//
$res = $r->query('example.com', 'A');
```

--------------------------------

### NetDNS2 TSIG Authentication for Notifications

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Demonstrates how to authenticate DNS NOTIFY requests using TSIG with NetDNS2. This requires the key name and secret to be configured correctly on the server.

```PHP
$n = new \NetDNS2\Notifier('netdns2.com', ['nameservers' => [ '192.168.0.1' ]]);

//
// add a TSIG to authenticate the request
//
$n->signTSIG('mykey', '9dnf93asdf39fs');

//
// trigger a notify request
//
$n->notify();
```

--------------------------------

### Check for Non-existent TXT Record

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Check if a domain does NOT have any TXT records using the Updater object.

```php
$u->checkNotExists('example.com', 'TXT');
```

--------------------------------

### Enable N3U EDNS Option

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Enables the NSEC3 Unificaiton (N3U) EDNS option, specifying the supported NSEC3 algorithms. This is part of the features defined in RFC 6975.

```php
//
// n3u(boolean enable, array supported_nsec3_algorithms)
//
$r->edns->n3u(true, [ 6, 7 ]);
```

--------------------------------

### NetDNS2 SIG(0) Authentication for Zone Transfers

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Illustrates how to authenticate zone transfer (AXFR) requests using SIG(0) with NetDNS2. This requires a valid private key file path and the OpenSSL extension.

```PHP
$r = new \NetDNS2\Resolver([ 'nameservers' => [ '192.168.0.1' ]]);

//
// add a SIG(0) to authenticate the request
//
$r->signSIG0('/etc/named/Kexample.com.+001+15765.private');

//
// request the zone transfer
//
$res = $r->query('example.com', 'AXFR');
```

--------------------------------

### Trigger DNS Notify Request

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Execute the DNS notify request with the configured records and TSIG authentication.

```php
$n->notify();
```

--------------------------------

### Enable DNS Name Server Identifier (NSID) EDNS Option

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

This snippet shows how to enable the DNS Name Server Identifier (NSID) EDNS option as defined in RFC 5001. This allows requesting information about the name server.

```php
//
// nsid(boolean enable)
//
$r->edns->nsid(true);
```

--------------------------------

### Allow Unverifiable DNSSEC Results

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Set the 'dnssec_cd_flag' to true to allow the upstream resolver to return DNS records even if they are not cryptographically verifiable. Use with caution.

```php
//
    // allow unverifiable DNSSEC results
    //
    $r->dnssec_cd_flag = true;

```

--------------------------------

### Enable DNS Zone Version EDNS Option

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Enables the DNS Zone Version EDNS option as defined in RFC 9660. This option can be used to query for the version of a DNS zone.

```php
//
// zone_version(boolean enable)
//
$r->edns->zone_version(true);
```

--------------------------------

### Enable DAU EDNS Option

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Enables the DNSSEC Answer Unificaiton (DAU) EDNS option, specifying the supported DNSSEC algorithms. This is part of the features defined in RFC 6975.

```php
//
// dau(boolean enable, array supported_dnssec_algorithms)
//
$r->edns->dau(true, [ 9, 10, 16 ]);
```

--------------------------------

### Add DNS Record

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Add a new DNS record to be updated using the Updater object.

```php
$u->add(\NetDNS2\RR::fromString('test.example.com 600 IN A 2.2.2.2'));
```

--------------------------------

### Querying DNS with Internationalized Domain Names (IDN)

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Queries DNS for a Unicode domain name. NetDNS2 converts the name to Punycode internally and back to Unicode for display if the PHP Intl extension is available.

```php
$res = $r->query('域名.中国', 'CNAME');

echo "域名.中国 resolves to: " . $res->answer[0]->cname;
```

```php
echo "The name value is: " . $res->answer[0]->name;
```

--------------------------------

### DNSSEC Configuration Options

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

These options configure DNSSEC behavior for NetDNS2 requests. They control features like enabling DNSSEC, setting the AD and CD flags, and specifying the EDNS(0) payload size.

```php
'dnssec'    => false,

        //
        // set the DNSSEC AD (Authentic Data) bit on/off.
        //
        // this isn't used by client connections, as the upstream resolver is responsible
        // for verifying the DNSSEC signatures and setting this bit.
        //
        // boolean, defaults to false
        //
        'dnssec_ad_flag'    => false,

        //
        // set the DNSSEC CD (Checking Disabled) bit on/off
        //
        // this instructs the upstream resolvers to validate DNSSEC signatures in the
        // response (when the dnssec option is true).
        //
        // if set to true, it signals the upstream resolvers to return the DNS records
        // regardless of whether they are cryptographically verifiable. 
        //
        // boolean, defaults to false
        //
        'dnssec_cd_flag'    => false,

        //
        // the EDNS(0) UDP payload size to use when making DNSSEC requests; see RFC 2671 
        // section 6.2.3 for more details
        //
        // integer, defaults to 1280
        //
        'dnssec_payload_size'   => 4000
```

--------------------------------

### Performing IPv6 Reverse DNS Lookup

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Performs a reverse DNS lookup (PTR record) for an IPv6 address.

```php
$res = $r->query('::1', 'PTR');

1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa. 86400 IN PTR localhost.
```

--------------------------------

### Enable TCP Keepalive EDNS Option

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Enables the TCP Keepalive EDNS option, specifying an idle timeout in units of 100 milliseconds. This option is only meaningful when 'use_tcp' is also set to true.

```php
//
// tcp_keepalive(boolean enable, int timeout)
//
$r->edns->tcp_keepalive(true, 300);
```

--------------------------------

### Client-side DNSSEC Signature Verification

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Perform full DNSSEC chain-of-trust validation locally using the NetDNS2\DNSSEC\Validator class. Requires 'ext-openssl' and optionally 'ext-sodium'.

```php
try
{
    $r = new \NetDNS2\Resolver(['nameservers' => [ '1.1.1.1' ]]);
    $r->dnssec = true;

    //
    // create a validator and load the built-in IANA root trust anchors
    //
    $v = new \NetDNS2\DNSSEC\Validator($r);
    $v->useRootTrustAnchor();

    //
    // query and validate — throws \NetDNS2\Exception on any failure
    //
    $res = $r->query('example.com', 'A');
    $v->validate($res);

    echo "signature chain verified successfully\n";

} catch(\
```

```php
\NetDNS2\Exception $e
{
    echo "DNSSEC validation failed: " . $e->getMessage() . "\n";
}

```

--------------------------------

### Check if Name is in Use

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Check if a given name is currently in use by any resource record using the Updater object.

```php
$u->checkNameInUse('test.example.com');
```

--------------------------------

### Querying DNS and Accessing IPv4 Address

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Performs a DNS query for an A record and accesses the resolved IPv4 address. The address is an instance of \\NetDNS2\\Data\\IPv4 and can be echoed directly or converted to a string using value() or strval().

```php
$res = $r->query('facebook.com', 'A');

echo "facebook resolves to: " . $res->answer[0]->address;
```

```php
echo $res->answer[0]->address;
```

```php
do_something($res->answer[0]->address->value());
```

```php
do_something(strval($res->answer[0]->address));
```

--------------------------------

### Enable DHU EDNS Option

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Enables the DNSSEC Hash Unificaiton (DHU) EDNS option, specifying the supported hash algorithms. This is part of the features defined in RFC 6975.

```php
//
// dhu(boolean enable, array supported_hash_algorithms)
//
$r->edns->dhu(true, [ 2, 3, 4]);
```

--------------------------------

### Remove Client Subnet EDNS Option

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Demonstrates how to disable a previously added EDNS option, specifically the client subnet option, before executing a DNS query. This is useful for changing your mind about including specific EDNS data.

```php
//
// create a new Resolver object
//
$r = new \NetDNS2\Resolver([ 'nameservers' => [ '192.168.0.1' ]]);

//
// enable the client subnet option, and pass in my IP range
//
$r->edns->client_subnet(true, '10.10.10.0/24');

//
// change my mind, and remove the option
//
$r->edns->client_subnet(false);

//
// request the A record
//
$res = $r->query('example.com', 'A');
```

--------------------------------

### Enable Expire EDNS Option

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Use this snippet to enable the 'expire' EDNS option, as defined in RFC 7314. This option relates to the expiration of DNS records.

```php
//
// expire(boolean enable)
//
$r->edns->expire(true);
```

--------------------------------

### Enable Cookie EDNS Option

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

This snippet shows how to enable the EDNS Cookie option, as per RFC 7873. The cookie value should be a 16-character hex-encoded string representing an 8-byte value.

```php
//
// cookie(boolean enable, string cookie_string)
//
$r->edns->cookie(true, '3132333435363738');
```

--------------------------------

### Check if Name is Not in Use

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Check if a given name is NOT in use by any resource record using the Updater object.

```php
$u->checkNameNotInUse('test.example.com');
```

--------------------------------

### Add Custom Trust Anchor for DNSSEC Validation

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Manually add a trust anchor for private or split-horizon zones to the DNSSEC Validator. Supports RSA, ECDSA, and ED25519 algorithms.

```php
$v->addTrustAnchor(\NetDNS2\RR::fromString(
        'internal. 0 IN DS 12345 8 2 <hex-digest>'
    ));

```

--------------------------------

### Check for Existing MX Records

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Check if a domain has any MX records using the Updater object.

```php
$u->checkExists('example.com', 'MX');
```

--------------------------------

### Enable DNS Error Reporting Channel EDNS Option

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Use this snippet to enable the DNS Error Reporting channel option, specifying an agent domain, as defined in RFC 9567.

```php
//
// report_channel(boolean enable, string agent_domain)
//
$r->edns->report_channel(true, 'example.com');
```

--------------------------------

### Delete All Records for a Domain

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Delete all resource records for a specified domain using the Updater object.

```php
$u->deleteAll('example.com');
```

--------------------------------

### Enable Extended Error EDNS Option

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Enables the Extended DNS Errors EDNS option as defined in RFC 8914. This allows for more detailed error reporting from DNS servers.

```php
//
// extended_error(boolean enable)
//
$r->edns->extended_error(true);
```

--------------------------------

### Check for Specific RR Existence

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Check if a specific resource record exists using the Updater object.

```php
$u->checkValueExists(\NetDNS2\RR::fromString('test.example.com 600 IN A 2.2.2.2'));
```

--------------------------------

### Delete DNS Record

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Delete a specific DNS record using the Updater object.

```php
$u->delete(\NetDNS2\RR::fromString('test.example.com 600 IN A 2.2.2.2'));
```

--------------------------------

### Delete All MX Records

Source: https://github.com/mikepultz/netdns2/blob/master/README.md

Delete all MX records for a given domain using the Updater object.

```php
$u->deleteAny('example.com', 'MX');
```

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