Question

I have a string like this:
(…1 (…2 DS(…3 ( …4 ) ) ) )

Which the best idea to find data in DS brackets if I don’t know how much brackets after DS before it end? (3, 4)
Its like math: multiply ds on the 3 and 4 brackets.

Answer 1

It can not be done by regular expression. Its not a regular language. Its general parsing.

$data  = '(...1 (...2 DS(...3 ( ...4 ) 5) )6 )';
$num   = array();
$start = strpos($data, 'DS') + strlen('DS');
$end   = strlen($data) - 1;
$paren = 0;
for ($i = $start;$i <= $end;$i++) {
    $n = $data[$i];
    if ($n == '(') $paren++;
    if ($n == ')') $paren--;
    if ($paren >= 0 && is_numeric($n)) {
        $num[] = $n;
    }
}
print_r($num);

output

Array
(
    [0] => 3
    [1] => 4
    [2] => 5
)