Alexandar Tzanov's Personal Blog

Function: get_dnr_hostmaster

The get_dnr_hostmaster PHP function will return the hostmaster email address for a domain name.

Get_dnr_hostmaster works on the assumption that the supplied domain already exists and is hosted somewhere. Confirm by using the php function gethostbyname.

Source Code

/* get_dnr_hostmaster
 * Developer: Alexandar Tzanov
 * Revised: 2013-08-05
 * Version: 1.0

function get_dnr_hostmaster($domain = '')
    // Ensure that a value was provided.
    if (!empty($domain))
        // Prepare the CLI string and execute it.
        $digup = "dig $domain SOA";
        exec($digup, $NSResult);
        /* We are only interested in lien 11 of the output. It is the line with
         * the answer to our question. We will split the line using tabs and
         * then spaces, since those are the delimiters for the line.
         * After the first split we need to remove any empty elements of the
         * array. We also need to check if the $answerSection array has 4
         * or 3 keys. This variation appear based on the domain name lenght.
        $answerSection = explode("\t",$NSResult[11]);
        $answerSection = array_values(array_filter($answerSection));
        $answerSectionArrayKey = (array_key_exists(4, $answerSection)) ? 4 : 3;
        $answerSection = explode(' ', $answerSection[$answerSectionArrayKey], 3);
        // Remove the trailing period
        $unformatedEmailAddress = rtrim($answerSection[1], '.');
        /* Since there is no way to know the username convention, e.g. there is
         * a period in it, we will assume that there isn't one. We will replace
         * the first period in the string with an @ sign.
        $emailAddress = preg_replace('/\./', '@', $unformatedEmailAddress, 1);
        return $emailAddress;
        return 'WARNING: Missing domain name!';


string get_dnr_hostmaster( string $domain )


Name Definition Default Value
$domain The domain name for which to return the Hostmaster email address. N/A


The get_dnr_hostmaster function will return the DNS record email address, e.g., ready to use. If no target domain is supplied a warning message will be returned.


$targetDomain = ""; // Set the domain to check.

// Make sure the domain exists and is hosted.
if (gethostbyname($targetDomain) != $targetDomain)
    // Get the Hostmaster email address.
    $hostmasterEmailAddress = get_dnr_hostmaster($targetDomain);
    // Say hello to the Hostamster.
    @mail($hostmasterEmailAddress, '', "Hello World!\n");

Revision History

Date Version Changes
2013-08-05 01.00.00 Initial release.

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