$re = '/^h[1,3,5]-f5(?:lb|gtm)01-s\.eset\.com$/mi';
$str = 'h1-f5lb01-s.eset.com
h1-f5gtm01-s.eset.com
h3-f5lb01-s.eset.com
h3-f5gtm01-s.eset.com
h5-f5lb01-s.eset.com
h5-f5gtm01-s.eset.com';
preg_match_all($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