1- Is domain name taken
<?php
$recordexists = checkdnsrr(“www.yahoo.com”, “ANY”);
if ($recordexists) 
echo “The domain name has been taken. Sorry!”;
else echo”The domain name is available!”;
?>

2- Get IP address
<?php
$ip = “204.71.200.75”;
$host = “www.yahoo.com”;
$verify_ip = gethostbyaddr($ip);
$verify_name = gethostbyname($host);
echo “$ip resolves to $verify_ip”;
echo “$host resolves to $verify_name”;
?>

3- Port scan
<?php
// set time to complete the task
ini_set(“max_execution_time”,60);
$rangeStart = 0;
$rangeStop = 1024;
$target = “www.yahoo.com”;
$range =range($rangeStart, $rangeStop);
echo “Scan results for $target”;
foreach ($range as $port) {
$result = @fsockopen($target, $port,$errno,$errstr,1);
if ($result)
echo “Socket open at port $port”;
}
?>