root/trunk/lib/Tag.class.php

<?php
 
class Tag
{
  public static function normalize($tag)
  {
    $n_tag = strtolower($tag);

    // remove all unwanted chars
    $n_tag = preg_replace('/[^a-zA-Z0-9]/', '', $n_tag);

    return trim($n_tag);
  }

  public static function splitPhrase($phrase)
  {
    $tags = array();
    $phrase = trim($phrase);

    $words = preg_split('/(")/', $phrase, -1, PREG_SPLIT_NO_EMPTY | PREG_SPLIT_DELIM_CAPTURE);
    $delim = 0;
    foreach ($words as $key => $word)
    {
      if ($word == '"')
      {
        $delim++;
        continue;
      }
      if (($delim % 2 == 1) && $words[$key - 1] == '"')
      {
        $tags[] = trim($word);
      }
      else
      {
        $tags = array_merge($tags, preg_split('/\s+/', trim($word), -1, PREG_SPLIT_NO_EMPTY));
      }
    }

    return $tags;
  }
}

?>