使用文本文件作为preg_match_all php的模式

Question

嘿，我正在为一个学校项目制作一个单词传感器，我似乎无法让preg_match过滤掉字符，如$，％，*，1-9和其他我试过的特殊字符w，\ W，[W] +但以下似乎都不起作用

$lines=array();
  $fp=fopen('Bad.txt', 'r');
  while (!feof($fp))
  {
    $line=fgets($fp);
    //process line however you like
    $line=trim($line);
    //add to array
    $lines[]=$line;
  }
    fclose($fp);
    $string = Input::get('comments');
    $matches = array();
    $matchFound = preg_match_all(
      "/\b(" . implode($lines,"|") . ")\b/i", 
            $string, 
            $matches
          );
    if ($matchFound) {
      $this->addError("The following is not allowed please change it.");
      $words = array_unique($matches[0]);
      foreach($words as $word) {
        echo "<li>" . $word . "</li>";
      }
      echo "</ul>";
    }