how to get a valid substring from bbcode post

Question

The idea is to have first 80 characters of user post visible in some overview mode. But how do I do that with bbtags?

• how not to cut string in the middle of bbtag
• how not to just open tag.
• I cannot just ignore those tags, because one of them is spoiler :-) (i could ignore simple formatting)

I have absolutely no clue how to do it and quick googling didn't help.

example:

Darth Vader [spoiler]is father of luke skywalker[/spoiler]

If I want substring of 20 characters, I would want this:

Darth Vader [spoiler]is fathe[/spoiler]

Answer 1

Maybe you help this code, it should be further developed, but the idea should be clear:

$str = 'Darth Vader [spoiler]is father of luke skywalker[/spoiler]';

function parse($str, $count)
{
    $arr1 = str_split($str);
    $result = [];
    $i = 0;
    $open = false;
    foreach ($arr1 as $chr)
    {
        if ($open || $chr === '[')
        {
            $open = true;
            if ($chr === ']')
            {
                $result[] = $chr;
                $open = false;
            }
            else
            {
                $result[] = $chr;
            }
        }
        elseif($i <= $count)
        {
            $result[] = $chr;
            $i++;
        }
    }
    return implode($result);
}
echo parse($str, 20);

You must rewrite code, and test with this case: "][" and "[][[[[[]]][[]][[[["

Or select other algoritm, and use regex....