PHP/DNS/DNS Functions

DNS Lookup Functions

 
Name                   Description
gethostbyname()        Gets IP address corresponding to the hostname
gethostbynamel()       Gets list of IP addresses corresponding to the hostname
gethostbyaddr()        Gets hostname corresponding to an IP address
getmxrr()                Fetches the mail exchange (MX) record associated with a hostname
dns_get_mx()             Alias for getmxrr()
checkdnsrr()             Checks for the existence of DNS records for a hostname
dns_check_record()       Alias for checkdnsrr()
dns_get_record()         Fetches DNS records associated with a hostname
<?php
$ip = gethostbyname("www.example.ru");
echo "IP = $ip\n";
$host = gethostbyaddr("192.0.34.166");
echo "Host = $host\n";
$ip = gethostbynamel("yahoo.ru");
print_r($ip);
?>

DNS Record Types and Their Meanings

 
A           Address code, used for storing an IP address associated with the domain
 
MX          Mail exchange, the domain name used for sending and receiving mail
 
NS          The authoritative name server
 
SOA         Start of Authority
 
PTR         Domain name pointer
 
CNAME       Canonical name for a DNS alias
 
AAAA        Address code used for IPv6 Addresses
 
ANY         Any of the above

Fetches DNS records associated with a hostname

 
<?php
$record = dns_get_record("php.net");
print_r($record);
?>

Performing DNS Lookups

 
gethostbyname() gets IP address corresponding to the hostname 
gethostbynamel() gets list of IP addresses corresponding to the hostname 
gethostbyaddr() gets hostname corresponding to an IP address 
getmxrr() fetches the mail exchange (MX) record associated with a hostname 
dns_get_mx() alias for getmxrr() 
checkdnsrr() checks for the existence of DNS records for a hostname 
dns_check_record() alias for checkdnsrr() 
dns_get_record() fetches DNS records associated with a hostname 
<?php
$ip = gethostbyname ( "www.wbex.ru" );
echo "IP = $ip\n";
$host = gethostbyaddr ( "192.0.34.166" );
echo "Host = $host\n";
$ip = gethostbynamel ( "yahoo.ru" );
print_r ( $ip );
?>

Using the dns_check_record() Function

 
<?php
    $hostname = "google.ru";
    if(dns_check_record($hostname, "NS")) {
        echo "An authoritative name server exists.\n";
    } else {
        echo "No name server was found for this domain\n";
    }
?>