<?php
function nslookup($domain, $nameserver) {
    $cmd = "nslookup -querytype=A $domain $nameserver";
    $output = shell_exec($cmd);
    return $output;
}

$nameservers = array("ns111.mschosting.com","ns185.mschosting.com");

if(isset($_POST['domains'])) {
    $domain = $_POST['domains'];
    $result = nslookup($domain, $nameservers);
    echo nl2br($result);
}
?>

<form method="post" action="">
    <textarea name="domains" placeholder="Enter domain here" rows="5" cols="40"></textarea><br>
    <input type="submit" value="Submit">
</form>