$post_content = "@jb51和@twitter在研究用#PHP#的#正则表达式#过滤话题和对象名";
$tag_pattern = "/\#([^\#|.]+)\#/";
preg_match_all($tag_pattern, $post_content, $tagsarr);
$tags = implode(',',$tagsarr[1]);
$user_pattern = "/\@([a-zA-z0-9_]+)/";
$post_content = preg_replace($user_pattern, '<a href="http://twitter.com/${1}">@${1}</a>', $post_content );
$post_content = preg_replace($tag_pattern, '<a href="http://twitter.com/search">#${1}#</a>', $post_content);