Explode string when not between ()

You need to use preg_split which splits the input according to the given regex.

$words = preg_split('~,(?![^()]*\))~', $str);
print_r($words);

DEMO

Explanation:

• , matches all the commas, only if it's not
• followed by any char but not of ( or ), zero or more times
• and further followed by a closing bracket.

If you change (?! to (?=, it does the opposite of matching all the commas which are present inside the brackets.