$re = '%[^,\[\]]+(?=(?:\[|,))%';
$str = 'DOG,THIS[3.8418],DOPE[4.7699],REACXH[3.2852000000000006],RACKET[0.8865999999999999],0321859[2.898411]';
preg_match_all($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