Subdomain availability

I am looking for a script that can see if the subdomain is available, for example here is some code that i thought might do it, but it does not appear to work does anyone have any ideas

<form action="<?php echo $PHP_SELF; ?>" method="post">
<input name="sub" type="text">.bbi.cc<br>
<input name="" type="submit">
</form>
<?
$hostname = "".$_POST['sub'].".bbi.cc";
$hosts = gethostbynamel($hostname);
if (is_array($hosts)) {
    if (count($hosts) == 1){
    echo "Sub Domain Taken";
    }
    elseif (count($hosts) > 1){
    echo "Sub Domain Available";
    }
}
?>

Code (markup):

 

here you have two possible situations:

1. no wildcard dns entry, every subdomain have an own DNS entry. Here you can use checkdnsrr() to check for a free subdomain.

2. wildcard dns entry, then a subdomain can have an own entry, or its managed over die wildcard DNS entry. If the wildcard is used, you have to grap and analyse the subdomains.

need you a script only for one special domain or to check subdomain from many different domains?

 

If using wildcard DNS why not just track when a subdomain is created and destroyed in a database. As long as you keep track correctly of this there shouldn't be any issues.

 

but that works only for own domains...