regular expression on string into array

The regular expression would be something like this: (.*?) \([^)]*\),? It uses . (anything) because you requested so, but if it's a word you should use \w instead, or if it's anything but whitespace \S so it would be something like this: (\S*) \([^)]*\),?

Explaining the expression:

• (.*?) - match anything, but in lazy mode, or 'as little as possible' mode
• [^)]* - match anything but ) as many as possible
• \([^)]*\) - match a pair of brackets and it's content
• ,? - match a comma if it's there

You can test it all these HERE

Finally, using the preg_match_all PHP function, this would look something like this:

$str = 'something (this1), something2 (this2), something3 (this3)';
preg_match_all('/(\S*) \([^)]*\),?/', $str, $matches);
print_r($matches);

I wouldn't use regular expressions for something like this, but rather just PHP's explode() function.

$string = "something (this1), something2 (this2), something3 (this3)";
$parts = explode(', ', $string);
$result = array_map(function($element) {
    return current(explode(' ',$element));
}, $parts);
print_r($result);

The above would output

Array
(
    [0] => something
    [1] => something2
    [2] => something3
)