$re = '/EXT-ID\[(?<ext_id>[^\]]+)\]\s+FLD\[(?<fld>[^\]]+)\]\s+FRMT\[(?<frmt>[^\]]+)\]\s+LL\[(?<ll>[^\]]+)\]\s+LEN\[(?<len>[^\]]+)\]\s+DATA\[(?<data>[^\]]+)\]/m';
$str = '+EXT-ID[3.1] FLD[Transaction Type] FRMT[FIXED] LL[0] LEN[2] DATA[26]
+EXT-ID[3.2] FLD[From Account Type] FRMT[FIXED] LL[0] LEN[2] DATA[00]
+EXT-ID[3.3] FLD[To Account Type] FRMT[FIXED] LL[0] LEN[2] DATA[00]
EXT-ID[19] FLD[Acquiring Institution ..] FRMT[FIXED] LL[0] LEN[3] DATA[702]
EXT-ID[43] FLD[Card Acceptor Name or ..] FRMT[FIXED-Group] LL[0] LEN[40] DATA[PAYPAL*GORTON STEPHANIE KSydney AU]
+EXT-ID[43.1] FLD[43-1 ATM Location] FRMT[FIXED] LL[0] LEN[25] DATA[PAYPAL*GORTON STEPHANIE K]
+EXT-ID[43.2] FLD[43-2 City Name] FRMT[FIXED] LL[0] LEN[13] DATA[Sydney ]
+EXT-ID[43.3] FLD[43-3 Country Code] FRMT[FIXED] LL[0] LEN[2] DATA[SG]
EXT-ID[48] FLD[Additional Data, Priva..] FRMT[LVAR-Bin] LL[1] LEN[11] DATA[OCT 0901]
EXT-ID[49] FLD[Currency Code, Transac..] FRMT[FIXED] LL[0] LEN[3] DATA[840]';
preg_match_all($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