BBCode

<?php
function replaceNestedTagsT($text, $openTag, $closeTag, $tagName)   {

    // Zjisti pocet tagu a offsety
    preg_match_all('~'.str_replace('~','\~',$openTag['search']).'~i', $text, $matchesOpen, PREG_OFFSET_CAPTURE | PREG_PATTERN_ORDER);
    preg_match_all('~'.str_replace('~','\~',$closeTag['search']).'~i', $text, $matchesClose, PREG_OFFSET_CAPTURE | PREG_PATTERN_ORDER);
    $found = array_merge($matchesOpen[0], $matchesClose[0]);
    if (empty($found))
        return $text;
    $queue = array();
    foreach ($found as $item)
        $queue[$item[1]] = $item[0];
    ksort($queue);

    // Oprav neuzavrene tagy
    $depth = 0;
    $offsetFix = 0;
    foreach($queue as $offset=>$tag)    {
        $level = substr($tag,1,1) == '/' ? -1 : 1; // Koncovy nebo zacatecni tag?
        if ($depth == 0 && $level == -1)    {
            $text = substr_replace($text, '', $offset-$offsetFix, $ln = strlen($tag));
            $offsetFix += $ln;
            continue;
        }
        $depth += $level;
    }
    if ($depth > 0)
        $text = substr_replace($text, str_repeat("[/$tagName]", $depth), $offset-$offsetFix+strlen($tag), 0);

    // Nahrazeni tagu HTML
    $text = preg_replace('~'.str_replace('~','\~',$openTag['search']).'~i', $openTag['replace'], $text);
    $text = preg_replace('~'.str_replace('~','\~',$closeTag['search']).'~i', $closeTag['replace'], $text);
    return $text;
}

function replaceNestedTagsM($text, $openTag, $closeTag)
{
    return preg_replace_callback('~' . str_replace('~', '\~', $openTag[0]) . '(.+)' . str_replace('~', '\~', $closeTag[0]) . '~is',
        function (array $m) use ($openTag, $closeTag) {
            return sprintf($openTag[1], $m[1]) . replaceNestedTagsM($m[2], $openTag, $closeTag) . $closeTag[1];
        },
        $text
    );
}

function replaceNestedTagsA($text, $openTag, $closeTag)    {

    $c = 0;
    do
    {
        $text = preg_replace(
            '~' . str_replace('~', '\~', $openTag[0]) . '(.+)' . str_replace('~', '\~', $closeTag[0]) . '~is',
            "$openTag[1]\\2$closeTag[1]",
            $text,
            -1,
            $c
        );
    }
    while ($c > 0);
    $text = preg_replace("~$openTag[0]|$closeTag[0]~", '', $text);
    return $text;
}

$text = <<<EOS
[quote]
    [quote=Tori]
        Lorem ipsum.
    [/quote]
    Dolor sit amet.
[/quote]
blablabla
EOS;


$m = microtime(TRUE);
for($i = 0; $i < 1e5; $i++) {
    $openTag = array('\[quote(?:=([^\]]+))?\]', '<div class="quote"><b>Citace %s</b><br>');
    $closeTag = array('\[/quote\]', '</div>');
    replaceNestedTagsM($text, $openTag, $closeTag);
}
echo 'Majkl: '.(microtime(TRUE) - $m);
echo "\n";

$a = microtime(TRUE);
for($i = 0; $i < 1e5; $i++) {
    $openTag = array('\[quote(?:=([^\]]+))?\]', '<div class="quote"><b>Citace $1</b><br>');
    $closeTag = array('\[/quote\]', '</div>');
    replaceNestedTagsA($text, $openTag, $closeTag);
}
echo 'Alphard: '.(microtime(TRUE) - $a);
echo "\n";


$t = microtime(TRUE);
for($i = 0; $i < 1e5; $i++) {
    $openTag = array('search'=>'\[quote(?:=([^\]]+))?\]', 'replace'=>'<div class="quote"><b>Citace $1</b><br>');
    $closeTag = array('search'=>'\[/quote\]', 'replace'=>'</div>');
    replaceNestedTagsT($text, $openTag, $closeTag, 'quote');
}
echo 'Tori: '.(microtime(TRUE) - $t);
echo "\n";