php给一组指定关键词添加span标签的方法

// Example use: $spanned = codeWords($string_containing_keywords);
// My site: andrew.dx.am
// Using colour==blue, but different arrays of words and different 
// colours can be added.
function onlyWholeWords(&$value, $key) {
// Ignores words after // comment delimiters.
//$value = "/\b(" . $value . ")\b/";  // doesnt handle comments
//$value = "/^(?:(?!\/\/).)*\K\b(" . $value . ")\b/"; 
// \K lookbehind alternative is not supported in PHP < 5.2.4, so use:
  $value = "/^((?:(?!\/\/).)*)\b" . $value . "\b/";
}
function addSpan(&$value, $key, $color=blue) {
  $value = "$1<span style=color:$color>" . $value . "</span>";
}
function codeWords($code) {
  $keywords = array(as, break, case, class,
  continue, default, do, elif, else,
  elseif, for, foreach, function, if, 
  new, null, return, self, switch,
  this, to, typeof, until,
  var, void, while, with);
  $keywords2 = $keywords;
  array_walk($keywords, onlyWholeWords);
  array_walk($keywords2, addSpan, blue);
  $code = preg_replace($keywords, $keywords2, $code);
  return $code;
}