<?php
echo "Enter url :";
$url = readline(">> ");
// Validate url
if(filter_var(gethostbyname($url), FILTER_VALIDATE_IP))
{
   echo("$url is a valid URL\n");
   $myfile = fopen("/etc/hosts", "a") or die("Unable to open file!");
   fwrite($myfile, "127.0.0.1 $url\n");  
   fclose($myfile);
} else {
   echo("$url is not a valid URL\n");
}