更新正则表达式只匹配单个单词中的大写字符

Consider the following:

考虑以下：

$tweet = "RT @forunemagazine Comment here RT @foo Blah";

function _process_retweets($tweet) {
  preg_match('/RT +@[^ :]+:?(.*)/ui', $tweet, $retweets);
  if (count($retweets) > 0) {
    $tag = ' {RT} '; // In reality, output could also be {RT|id}, etc. 
                     // but this is not relevant here
    return preg_replace("/RT/ui", $tag, $tweet);
  }
  else {
    return $tweet;
  }
}

echo _process_retweets($tweet);
$tweet = "RT