broken regex for hostname from url

[thedaver]

I want to find the true hostname from the "host" returned by parse_url. In Unix / Linux / TCP/IP, a host's name is "

http://www"

from the hostname "

http://www.example.com".

I had the regex working, but I also needed to filter out any bozos who would erroenously enter "try.to.break.the.url.

http://www.example.com".

Again, I want to match/select the "

http://www"

hostname and can do without the rest. I thought that this code would work, but it doesn't.

Maybe some fresh eyes will spot my error. Thanks.

<?php

function real_host ($host=&quot;&quot {
if (! $host) {return (&quot;&quot;}

// This regex pair is belt-and-suspenders redundancy from
// my debug efforts. The first one should be sufficient
// to filter out bogus prefix's on the hostname, but it
// doesn't get the job done.....

if (preg_match(&quot;/^.*?\.?(.*)\.(.*)\.(.*)$/&quot;,$host,$matches))
{ if (preg_match(&quot;/^.*?\.?(.*)$/&quot;,$matches[1],$final))
{return $final[1];}
}
return (&quot;&quot;
}

$arr=&quot;&quot;;

// My objective is to return &quot;

http://www&quot;

from function real_host

$arr=parse_url(strtolower(&quot;

http://wrong.www.example.com/index.php&quot;));

print_r($arr);
print &quot;<br>\n&quot;;
print real_host($arr[&quot;host&quot;]);
?>

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[sleipnir214]

You have some assumptions wrong.

&quot;

http://www&quot;

is not the FQDN of a machine. &quot;

http://www.foo.com&quot;

is.

Although &quot;

http://www.foo.com&quot;

is a FQDN, it's also possible that &quot;foo.com&quot; can be, too. DNS will allow you to relate an IP address to &quot;foo.com&quot; for the purposes of IP resolution. What will your code do if the string &quot;

http://www&quot;

does not appear in the input URL?

It's also possible that &quot;foo.

http://www.foo.com&quot;

is the correct FQDN of a machine.

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TANSTAAFL!!