$re = '/(ABC-\d+,)(.*?(?=^ABC|\z))/ms';
$str = 'ABC-1,01/01/1974,X1,Y1,Z1,"RANDOM SINLGE LINE TEXT 1",
ABC-2,01/01/1974,X2,Y2,Z2,"THIS IS
A RANDOM
MULTI LINE
TEXT 2",
ABC-3,01/01/1974,X3,Y3,Z3,"THIS IS
ANOTHER RANDOM
MULTI LINE TEXT",';
preg_match_all($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