$re = '/^(.*):\s*Bus Number: Departure\s*\nBus code:\s*([^ ]+)\s([^ ]+)\s([^\n]+)[ \t]*(?:\n|$)((?:[^\n]+\n)+)?/m';
$str = 'KPN_Sleeper: Bus Number: Departure
Bus code: Kpn-866489 KA-01-7233 Bangalore dfdf
AC Sleeper/56 Seats
24 Seats booked
SRS: Bus Number: Departure
Bus code: SRS-5858 KA-31-5985 Bangalore dfdf dfd
SAM: Bus Number: Departure
Bus code: SAM-0077 TN-23-0777 Chennai ';
preg_match_all($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