$re = '/^(?:[^,]*, ){7}\'\K[^\']+\.gov(?=\')/m';
$str = '(2843, \'\', 0, \'\', \'\', \'\', \'\', \'mail@yahoo.gr\', \'\', \'\'),
(2844, \'\', 0, \'\', \'\', \'\', \'\', \'mail1@washpost.com\', \'\', \'\'),
(2845, \'\', 0, \'\', \'\', \'\', \'\', \'someMail@gmail.com\', \'\', \'\'),
(2846, \'\', 0, \'\', \'\', \'\', \'\', \'else@gmail.gov\', \'\', \'\'),';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php