用PHP解析类JSON字符串为数组的实现

题目：把字符串嵌套关系转换成数组,字符串只包含成对中括号、数字和逗号
字符串：(1,(1,2,(1,(1,2,(1)),3)),3,(1,(1,2,((1((1,(1,2,(1,2,3),4,5),3),2)),2)),((1,2,3),2,3),4,5),5)

程序：

$string = '(1,(1,2,(1,(1,2,(1)),3)),3,(1,(1,2,((1,((1,(1,2,(1,2,3),4,5),3),2)),2)),((1,2,3),2,3),4,5),5)';

$result = $previous = [];
$current = $number = null;

$i = 0;
while ( isset($string[$i]) ) {
    $value = $string[$i];

    switch ($value) {
        case '(':
            if ( is_null($current) ) {
                $current = &$result;
            } else {
                $previous[] = &$current;
                $current[] = [];
                $current = &$current[count($current) - 1];
            }
            break;
        case ')':
            if ( !is_null($number) ) {
                $current[] = intval($number);
                $number = null;
            }

            $last = count($previous) - 1;
            $current = &$previous[$last];
            array_pop($previous);
            break;
        case ',':
            if ( !is_null($number) ) {
                $current[] = intval($number);
                $number = null;
            }
            break;
        default:
            $number .= $value;
            break;
    }

    $i++;
}

echo json_encode($result);

输出结果：[1,[1,2,[1,[1,2,[1]],3]],3,[1,[1,2,[[1,[[1,[1,2,[1,2,3],4,5],3],2]],2]],[[1,2,3],2,3],4,5],5]