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checkdnsrr
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checkdnsrr

Name

checkdnsrr — Checks for DNS resource records for the given host.

Synopsis

bool checkdnsrr(host[, type]); string host: Hostname or IP address to check string type (optional): Type of record to check for

Returns

TRUE if a record can be found; FALSE on error

Description

Performs a DNS lookup on the specified host (either a hostname or IP address) and returns TRUE if a record of the specified type is found. This function can look up the following record types:

Record Type	Details
A	Address: Defined in RFC 1035.
ALL	Any of the valid types.
CNAME	Canonical Name: Defined in RFC 1035.
MX	Mail Exchanger: Defined in RFC 1035.
NS	Name Server: Defined in RFC 1035.
PTR	Pointer: Defined in RFC 1035.
SOA	Start of Authority: Defined in RFC 1035.

If no record type is specified, MX is assumed. For more information on DNS resource records, consult the documentation for your system's nslookup command and review the RFCs listed in the preceding table.

Note

checkdnsrr() doesn't support IPv6.

Version

PHP Version: 3+, 4+

Example

Example 830. Check whether a given domain name has an MX resource record

<?php
$url = "http://www.php.net/";
$component = parse_url ($url);
checkdnsrr ($component['host'], 'MX')
    or die ('No MX record exists for <i>$component[host]</i>.  Did you enter the URL correctly?');

echo "MX record found for <i>$component[host]</i>";
?>

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PHP Functions Essential Reference. Copyright © 2002 by New Riders Publishing (Authors: Zak Greant, Graeme Merrall, Torben Wilson, Brett Michlitsch). This material may be distributed only subject to the terms and conditions set forth in the Open Publication License, v1.0 or later (the latest version is presently available at http://www.opencontent.org/openpub/). The authors of this book have elected not to choose any options under the OPL. This online book was obtained from http://www.fooassociates.com/phpfer/ and is designed to provide information about the PHP programming language, focusing on PHP version 4.0.4 for the most part. The information is provided on an as-is basis, and no warranty or fitness is implied. All persons and entities shall have neither liability nor responsibility to any person or entity with respect to any loss or damage arising from the information contained in this book.