$re = '/VARIABLE.*?(?=VARIABLE|$)/s';
$str = 'VARIABLE: GRP1.SGRP1.100:VAR1
Timestamp (LOCAL_TIME),Value
2018-07-18 13:52:09.100,25582
2018-07-18 13:52:49.900,24048
VARIABLE: GRP1.SGRP2.102:VAR1
Timestamp (LOCAL_TIME),Value
2018-07-18 13:52:09.100,25582
2018-07-18 13:52:49.900,24048';
preg_match_all($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