which search engine can I use in order to handle ".com.au" domain name?

[henry]

I want to check the availability of domain name through some third party's interface.
e.g. I want to check whether or not "myweb.com" is registered, I can realize this function in PHP as follows:
$searcgEngine = 'http://whois.hichina.com/cgi-bin/whois?domain=myweb.com&GO=GO';
$fp = file_get_contents($searchEngine,'rb');
if(strstr($fp,"no matching record") || strstr($fp,"No match for")) return true;
else return false;

in this case, I use "hichina.com" as search engine, but it can't handle ".com.au" or ".org" domain name.
which search engine can I use in order to handle ".com.au" domain name?