note 54121 added to function.preg-match

Domain name parsing is tricky with an RE. The simplest, most efficient method, is probably just to split the domain by . and individually verify each part, like so: <?php $email_address = 'tom@rocks.my.socks.tld'; // An RE subject function verify_addr ($address) { $return = false; if (preg_match ('/^[\w.]+@([\w.]+)\.[a-z]{2,6}$/i', $address, $domain)) { $domain = explode ('.', $domain[0]); // Split the domain into sections wherein the last element is either 'co', 'org', or the likes, or the primary domain name foreach ($domain as $part) { // Iterate through the parts if (substr ($part, 0, 1) == '_' || substr ($part, strlen ($part) - 1, 1) == '_') $return = false; // The first or last character is _ else $return = true; // The parts are fine. The address seems syntactically valid } } return $return; } if (verify_addr ($email_address)) { // The address is good, what now? } else { // Address is invalid... Do something. } ?> An alternative would be to look for _. and ._ in the domain section, or to just ignore that restriction entirely and use this RE: /^[\w.]+@(?:[\w.]{2,63}\.)+[a-z]{2,6}$/i ---- Manual Page -- http://www.php.net/manual/en/function.preg-match.php Edit -- http://master.php.net/manage/user-notes.php?action=edit+54121 Delete: added to the manual -- http://master.php.net/manage/user-notes.php?action=delete+54121&report=yes&reason=added+to+the+manual Delete: bad code -- http://master.php.net/manage/user-notes.php?action=delete+54121&report=yes&reason=bad+code Delete: spam -- http://master.php.net/manage/user-notes.php?action=delete+54121&report=yes&reason=spam Delete: useless -- http://master.php.net/manage/user-notes.php?action=delete+54121&report=yes&reason=useless Delete: non-english -- http://master.php.net/manage/user-notes.php?action=delete+54121&report=yes&reason=non-english Delete: other reasons -- http://master.php.net/manage/user-notes.php?action=delete+54121&report=yes Reject -- http://master.php.net/manage/user-notes.php?action=reject+54121&report=yes Search -- http://master.php.net/manage/user-notes.php