$re = '/([a-zA-Z]+(?:[ \t]+[a-zA-Z]+)*)(?:[ \t]+(\d+)(?:[ \t]+(.+))?)?/m';
$str = 'Battery Bank 1
Battery Bank 1 Segments
Battery Bank 1 Warranty Logger
Battery Bank 10
Battery Bank 10 Segments
Battery Bank 10 Warranty Logger
BSU
BSU 1
PCS 3
PCS 1
System
System Meter';
preg_match_all($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