don't make two querys

[ptopenweb]

if you use "$whois_string = $this->info();" inside the isAvailable() function you are querying the whois server two times.

(example on the first page)
$whois_answer = $domain->info(); //FIRST QUERY
...
if ($domain->isAvailable()) { //SECOND QUERY

Some whois servers have limits of 1 host from one ip each second (for instance).
So you should only ask only one time.
You can for instance save the domain info in a class variable and use it, if already exists

[NabiKAZ]

I fixed this bug.
After accept pull request you can test it or you can get fork from here: https://github.com/NabiKAZ/php-whois/