$re = '/(interface)\s+([^!]+)/m';
$str = '!
interface TenGigabitEthernet 1/49
description Uplink
no ip address
switchport
no shutdown
!
interface TenGigabitEthernet 1/50
no ip address
shutdown
!
interface TenGigabitEthernet 1/51
no ip address
shutdown
!';
preg_match_all($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