quote.css does not work?

I checked, the $text does not contain '[quote' when passed in. Strange.

function _quote_filter_process($text) {
// Thanks: function based on code from punbb.org
if (strstr($text, '[quote')) {
$pre = '';
$post = '';
$markup = $pre . t('Quote:') . $post;
$text = str_replace(array('[quote]', '[quote=]', '[/quote]'), array($markup, $markup, $post), $text);
$text = preg_replace('#\[quote=(?:"|\')?(.*?)["\']?(?:"|\')?\]#s', $pre . t('%name wrote:', array('%name' => '\\1')) . $post, $text);
}
return $text;
}

Problem solved.
It was caused by the order of input filters. Since I enabled the bbcode filter and it was used before quote filter, the $text was first processed by bbcode filter, and then passed to quote filter. This is why the $text as input for quote filter did not contain '[quote' sub-string.

Meanwhile, I did not install "quicktags" module, so the bbcode filter did not give me enough indication for quotation.

Hang