working of regex to filter domain name

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0

could anyone expalin me how this is working what is the role of @ further there is nothing preceeding character before (?:http) then why "?' this is used since it means preceeding character must appeat once or not at all..

<?php
// get host name from URL
 preg_match('@^(?:http://)?([^/]+)@i',
  "http://ift.tt/13yRSMW", $matches);
$host = $matches[1];

// get last two segments of host name
preg_match('/[^.]+\.[^.]+$/', $host, $matches);
echo "domain name is: {$matches[0]}\n";
 ?> 

asked 31 secs ago

ASEN

25

working of regex to filter domain name