$re = '/(?:(?<exitingN>N)|((?<exitingF>[UMTREL]{1})(?<exitingNumber>[0-9]+)))-((?<enteringB>B)|(?:(?<enteringF>[UMTREL]{1})(?<enteringNumber>[0-9]+)))/m';
$str = 'N-U0 U0-M1
M1-T9 T9-R10 R10-E19
E19-L100 L100-B';
preg_match_all($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